BIOLOGY LIBRARY G THE DUBLIN DISSECTOR. OR .MANUAL OF ANATOMY ;* COMPRISING A DESCRIPTION OF THE BONES, MUSCLES, VESSELS, NERVES, AND VISCERA; THE RELATIVE ANATOMY OF THE DIFFERENT REGIONS OF THE HUMAN BODY, TOGETHER WITH THE ELEMENTS OF PATHOLOGY. BY ROBERT HARRISON, A.M. M.B. T.C.D. MEMBER OF, AND ONE OF THE PROFESSORS OF ANATOMY IN THE ROYAL COLLEGE OF SURGEONS IN IRELAND, AND ONE OF THE SURGEONS OF THE CITY OF DUBLIN HOSPITAL. SECOND AMERICAN, FROM THE FIFTH ENLARGED DUBLIN EDITION. WITH ADDITIONS BY ROBERT WATTS, JR. M.D. PROFESSOR OF ANATOMY IN THE COLLEGE OF PHYSICIANS AND SURGEONS IN THE CITY OF NEW YORK, &C. &C. NEW YORK: J. & H. G. LANGLEY, 57 CHATHAM STREET : PHILADELPHIA. HASWELL, BARRINGTON AND HASWELL ! BOSTON. WILLIAM D. TICKNOR. MDCCCXLIII. BIOLOGY LIBRARY G Entered, according to Act of Congress, in the year 1840, BY J. & H. G. LANGLEY, in the Clerk's Office of the District Court of the Southern District of New York. STEREOTYPED BY SMITH AND WRIGIFT, 216 WILLIAM ST. N. Y. R. CRAIGHEAD, PRINTER, 112 rULTOK ST. PREFACE. IN undertaking to prepare an American edition of the Dublin Dissector, the editor has been principally actuated by a desire to aid the publishers in placing within the reach of the medical students of this country, a work which he has long considered the best manual of Practi- cal Anatomy in our language. It was suggested by the publishers, that some additions might perhaps be made, which would enhance the value of the book, and it was left to the editor to decide what those additions should be : it should be distinctly understood, that the additions are merely compilations, principally from J. Cruveilhier, (Ana- tomie Descriptive, Paris 1834): Horner, (Treatise on Special and General Anatomy, Philadelphia 1836): Tie- demann ; and Gross on Pathological Anatomy, (Boston 1839): and that nothing can be claimed on the score of originality, it having been intended to select those facts which are of the most practical importance, and yet not to introduce so much new matter as to diminish the con- venience of the book as a dissecting room Manual. The classification of the muscles has been introduced, because in the performance of his public duties the editor has found something of the same kind very useful in im- pressing upon the minds of students their number, situa- tion, and functions ; the only muscles omitted in the clas- sification, are those of ordinary respiration, and those of the back, which are left as classed in the text, in which all are described in the order in which they are met with on dissection, which order has for that reason been left unchanged : the classification cannot be considered as original, and yet it would be difficult to give credit for it. It was deemed important to introduce the weights and measurements of the different internal organs, and to give the averages as nearly as possible, both in reference to * IV PREFACE. their normal condition, and to those changes in size and density which result from a morbid state. It also seemed proper in such a work, to introduce all the principal varie- ties which are met with in the muscular, arterial, and venous systems, and a good deal of pains has been taken particularly with the chapter on the arteries : there like- wise appeared to be a propriety in connecting with the description of each bone a table of the muscles arising from, and inserted into it, and in enumerating the fractures to which each is most commonly liable ; also in referring in the chapter on Articulations to those luxations not enu- merated by the author : in the Appendix a few additional directions are given on the subject of injections : in short, it has been the earnest endeavour of the editor to increase the value of the book to the practical student of anatomy. But few liberties have been taken with the text, and those principally where they were necessary to the continuity of sense in the text and the context ; most of the addi- tions are distinguished by a smaller type, and all of them except mere verbal alterations, are included in brackets [] ; in those cases where it seemed proper, reference has been made to anatomical preparations which are in the College Museum, or in private collections in this city. It is needless to offer any apology for the manner in which the editorial part of the work has been executed, as its merits and demerits will be judged of by the proper tribunal : the editor will be repaid for his labour should those for whose benefit it has been undertaken find the book not less useful to them, with the additions, than it was without them, to himself when a student. New York, 8tk October, 1840. CONTENTS. PART I. OF THE MUSCLES, VISCERA, ETC. CHAPTER I. ANATOMY OF THE EXTERNAL PARTS OF THE HEAD AND FACE. PAGE. EXTERNAL PARTS OF THE HEAD, 1 General remarks on muscles of head, division of, 2 Classification of the muscles of the head and face, ib. Occipito-frontalis, 3 Epicranial aponeurosis, ib. Structure, pathology, &c. of scalp, 5 External muscles of ear, 6 EXTERNAL FARTS OF FACE, ib. Division of muscles of, 8 Orbicularis palpebrarum, ib, Physiology, &c. of do -. 9 Tensor tarsi, or Homer's muscle, 10 Muscles of the nose, lips, &c ib. Buccinator muscle, 13 Division of glands in general, 14 Peculiarities of salivary glands, 15 Parotid gland, 16 Steno's duct, 17 Pathology of parotid gland, 19 Masseter, temporal and pterygoid muscles, ib. Temporal aponeurosis, 21 Motion of lower jaw, ib. Vessels and nerves of face, 25 CHAPTER II. ANATOMY OF THE NECK. Classification of the muscles of the neck, 27 General remarks on do , 31 VI CONTENTS. PAGE. Platysma, myoids, and cervical fascia, 32 Sterno-cleido-mastoid muscle, 34 Division of neck into triangular regions, 35 Sterno-hyoid and thyroid muscles, 36 Omo-hyoid muscle, 37 Thyroid body, ib. Physiology and pathology of, 38 Digastric muscle, 39 Sub-maxillary gland, 40 Whartonian duct, 42 Pathology of sub-maxillary gland, ib. Mylo-hyoid and genio-hyoid muscles, ib. Sublingual gland, ib. Hyo and genio-hyo-glossi muscles, ib. Styloid muscles, 43 Vessels and nerves of the neck, 44 MOUTH, 48 Tongue, 49 Pharynx, constrictors of ; openings in, 50 Palate, arches of; uvula, 54 Levator palati, tensor palati, palato-glossus, 55 Tonsils, or amygdalse, ib. Pathology of soft palate, tonsils, &c 56 (Esophagus, ib. Pathology of pharynx and oesophagus, 57 LARYNX, cartilages, muscles, &c. &c 58 Vessels and nerves of larynx, 62 Pathology of larynx and trachea, 63 Deep muscles of neck ; longus colli, &c 64 CHAPTER III. ANATOMY OF THE THORAX. Muscles on anterior and lateral parts of thorax, 66 Mammary gland, ib. Pathology of, ib. Pectoralis major, &c. &c 67 Serratus magnus, 69 Intercostal muscles, 70 Levatores costarum, triangulars sterni, 71 AXILLA, 72 CAVITY OF THE THORAX, 73 Mode of opening thorax, 74 Anterior mediastinum, ib. Pleura, 75 Ligamentum latum pulmonis, 76 Posterior mediastinum, ib. Vena azygos, 77 Thoracic duct, &c 78 LUNGS, 79 ^ Pathology of lungs and pleurae, 81 CONTENTS. Vll PAGE. Pericardium, 82 Pathology of, 83 HEART, 84 Pulmonary artery, , 8 : : 87 Ductus arteriosus, ib. Aorta, , 89 Description of the heart, 90 Pathology of heart, 91 Parts passing through upper orifice of thorax, 92 Trachea, 93 Bronchial glands, ib. CHAPTER IV. MUSCLES ON THE POSTERIOR PART OF THE TRUNK. Muscles of the back; ligamentum nuchae, Lumbar fascia, and trapezius, Latissimus dorsi, 97 Rhomboideus, 98 Levator anguli scapula and serrati postici, 99 Splenius, 100 Sacro-lumbalis, longissimus dorsi, and spinalis dorsi, ib. Cervicalis descendens, 101 Recti and obliqui capitis postici,.. 103 CHAPTER V. ANATOMY OF THE UPPER EXTREMITY. General remarks on the muscles of the upper extremity, 105 Classification of do ib. Fascia and superficial veins of the arms, 110 Deltoid muscle, Ill Supra and infra-spinatus muscles, 112 Teres minor and sub-scapula muscles, 113 Remarks on Capsular muscles of the shoulder joint, ib. Coraco-brachialis muscle, 114 Biceps, 115 Brachialis anticus, or externus, 116 Triceps, 117 Vessels and nerves of the arm, 119 Fore arm and hand, 120 Cutaneous veins, basilic, cephalic, median, &c ib. Fascia of fore arm, 121 Palmar fascia, ib. Palmaris brevis muscle, ib. Division of muscles of fore arm into pronators and flexors, . 122 Supinators and extensors, 127 Muscles of the hand, 131 Vessels and nerves of the fore arm and hand, 1. Till CONTENTS. CHAPTER VI. ANATOMY OP THE ABDOMEN AND PELVIS. PAGE. Superficial fascia of the abdomen, 136 *Obliquus externus, 138 Linea alba, 139 Linea semilunaris, and linea transversae, 140 External inguinal ring, and intercolumnar fascia, 141 Poupart's or Fallopius's ligament, ib. Gimbernaut's ligament and triangular ligament or fascia, 142 Obliquus internus or ascendens, 143 Cremaster muscle, 144 Transversalis, 145 Rectus muscle, 146 Pyramidal muscle and transversalis fascia, 147 Spermatic or inguinal canal, 148 HERNIA, ib. Oblique inguinal, ib. Direct or ventro-inguinal, 149 Femoral or crural, 150 Inguinal lymphatic ganglia, ib. Saphena vein, 151 Fascia lata, ib. Fascia iliaca, 153 Femoral or crural ring, 154 Fascia propria, ib. Measurements of parts engaged in hernia, 156 Regions of abdomen, ib. Peritoneum, 157 Omenta, meso-colons, &c 160 Division of viscera of abdomen, 164 Stomach, ib. Glandulas Brunneri, 166 Duodenum, 167 Jejunum, ilium, and caecum, or caput coli, 168 Ilio-colic valves, 169 Colon and rectum, 170 Structure of intestinal canal, 171 Glandulse aggregates or Peyeri, 172 Pathology of peritonaeum and abdominal viscera, 173 Gastro-enteric mucous membrane, 174 Liver, 176 Pathology of, 180 Gall bladder, 181 Pathology of, ib. Spleen, 182 Pathology of, 183 Pancreas, ib. |f Pathology of, 184 CONTENTS. IX PAGE. Vessels and nerves of the abdomen, 184 Kidney, 187 Ureter, 189 Renal capsule, or supra-renal or atrabiliary body, 190 Pathology of kidney, ib. Bladder, 208 Pathology of, 214 Urethra, 226 Diaphragm, 191 Muscles which assist in respiration, 194 Quadratus lumborum and psoae muscles, 195 Iliac muscles, 196 PERINEUM IN THE MALE, 197 Sphincter ani, superficial fascia, 198 Erector or compressor penis, 200 Accelerator urinae or ejacultaor seminis, &c. &c ib. Tri angular ligament of urethra, 202 Cowper's, or the anti-prostatic glands, ib. Levator ani muscle, 203 Compressores urethrse, or Wilson's muscles, 204 Surgical anatomy of parts concerned in lithotomy, 205 Pubic ligament, 206 Coccygeus muscle, ib. Triangular space on fundus of bladder, ib. Pelvic portion of peritonaeum, 207 Urinary bladder, 208 Pathology of, 214 Pelvic, obturator, and vesical fasciae, 209 Ligaments of the bladder, 210 Coats of the bladder 212 ORGANS OF GENERATION IN THE MALE, 215 Scrotum, , , ib. Dartos, superficial fascia, 216 Tunica vaginalis, albuginea, 217 Testicle, , 218 Epididymis, 219 Vas deferens, 220 Spermatic cord, 221 Vesiculae seminales, 222 Prostate gland, 223 Penis, 224 Urethra, 226 Method of injecting the penis and corpus spongiosum ure- thrse, 228 Pathology of testicle, 230 Pathology of vesiculse seminales and prostate gland, 231 X CONTENTS. CHAPTER VII. ORGANS OF GENERATION IN THE FEMAL13. PAGE. Vagina, uterus, &. &c 233 Fallopian tubes and ovaries, 236 Pathology of female organs of generation, 237 CHAPTER VIII. ANATOMY OF THE INFERIOR EXTREMITY. Classification of muscles of the inferior extremities, 238 Fascia lata, 243 Muscles on the forepart and sides of the thigh, 245 Tensor vaginae femoris, sartorius, triceps adductor, &c. &c ib. Vessels and nerves of the thigh, 252 Muscles on the posterior part of the thigh, 253 Glutseus maximus, medius, &c. &c 254 Pyriformis, obturator internus, externus, gemelli, &c. &c 256 Glutceal and sciatic vessels, <$-c 259 Sciatic nerve, ib. Hamstring muscles, 260 Popliteal space, ib. Leg ; fascia, sub-cutaneous veins and nerves, 264 Plantar fascia, 267 Muscles on the anterior and external part of the leg, ib. Anterior tibial vessels and nerves, 270 Muscles on the back of the leg, 271 Muscles of the foot, 275 Posterior tibial vessels and nerves, 281 PART II. OF THE NERVOUS SYSTEM. CHAPTER I. BRAIN, MEDULLA OB LONG ATA, AND ORIGIN OF THE CEREBRAL NERVES. BRAIN, 282 Dura mater, 283 Sinuses, 285 Arachnoid membrane, pia mater, 288 Cerebrum, 290 CONTENTS. XI PAGE. Ventricles, 293 Cerebellum, 299 MEDULLA OBLONGATA, 301 ORIGIN OF THE CEREBRAL NERVES, 302 CHAPTER II. ANATOMY OP THE MEDULLA SPINALIS, ETC. General view of cranial nerves, 306 Origin of the spinal nerves, 307 Dissection of the brain from below, 311 Structure of the cerebellum, 312 Structure of the cerebrum, ib. Vessels of the brain, Pathology of the brain and its membranes, 315 CHAPTER III. DISSECTION OF THE CEREBRAL SPINAL, AND GANGLI- ONIC NERVES. Olfactory, 317 Optic, 318 Third and fourth, 319 Ophthalmic nerve, ib. Lachrymal, frontal, and nasal nerves, 320 Sixth or abducens nerve, 321 Ophthalmic or lenticular ganglion, ib. Offices of orbital nerves, 322 Superior maxillary nerve, 323 Meckel's ganglion, ib. Palatine, spheno-palatine, naso-palaline, or nerve of Cotunnius, ib. Naso-palatine ganglion, ib. Vidian nerve, corda tympani, submaxillary ganglion, ib. Inferior maxillary nerve, 325 Inferior dental and gustatory nerves, 326 Facial nerve or portio dura, 327 Auditory nerve or portio mollis, 329 Glosso-pharyngeal nerve, ib. Pneumo-gastric nerve, ib. Pharyngeal plexus, 330 Laryngeal nerves, ib. Pulmonic plexuses, 331 CEsophageal plexus or plexus gulee, 332 Spinal accessory nerve, ib. Lingual nerve, ib. SPINAL NERVES, 333 Sub-occipital nerve, ib. Xll CONTENTS. PAGE. Cervical plexus, 334 Phrenic or internal respiratory nerve, ib. External respiratory nerve, 335 Brachial plexus, ib. Thoracic and scapular branches, 336 Internal cutaneous, external cutaneous, ib. Median or brachial, ulnar, musculo-spiral, &e 337 Dorsal nerves, 339 Nerves of Wrisberg 340 Lumbar nerves and plexus, ib. Inguino-cutaneous, anterior crural nerves, ib. Obturator, glutaeal, communicating, &c 34J Sacral nerves and plexus, 342 Lesser sciatic, inferior glutaeal, pudic nerves, &c 343 Great sciatic or posterior crural nerve, ib. SYMPATHETIC NERVES, 345 Cervical ganglions, 346 Cavernous or carotid ganglion, 347 Cardiac nerves, ib. Cardiac plexus, cardiac ganglion, 348 Thoracic ganglions, , 349 Splanchnic nerves, ib. Solar plexus, , 350 Lumbar glanglions, ib. Sacral or pelvic ganglions, ; 351 Ganglion impar, , ib. CHAPTER IV. ORGANS OF SENSE. Nose, 351 Taste, 354 Ear, 355 General view of muscles of the ear, , ib. Eustachian tube, 357 Bones of the ear, 358 Muscles of the ear, ib. Labyrinth, 359 Eye, 360 Muscles of the orbit, ib. Lachrymal apparatus, 363 Eyelids, 364 riorner's muscle, ib. Globe of the eye, 365 Skin, or the organ of touch, 371 Cellular membrane, 373 CONTENTS. Xlll PART III. ANATOMY OF THE VASCULAR SYSTEM. FA6E. ARTERIAL SYSTEM, 375 Aorta, ib. Coronary arteries, 376 Arteria innominata, , , 377 Carotid arteries, ib. External carotid, , 378 Superior thyroid, lingual, and labial, ib. Muscular, occipital, posterior, auricular, and pharyngeal, 380 Transverse facial, temporal, and internal maxillary, 381 Internal carotid, , 382 Ophthalmic and cerebral arteries, ib. Subclavian arteries, , 384 Vertebral, basilar, thyroid axis, internal mammary, &c 385 Axillary artery, 387 Brachial artery, 388 Profunda arteries, &c 389 Ulnar artery, , 390 Radial artery, 391 Thoracic aorta 392 Bronchial, oesophageal, and intercostal arteries, 393 Abdominal aorta, ib. Phrenic arteries, ib. Cffiliac axis, .... 394 Mesenteric and renal arteries, 395 Spermatic, lumbar and middle sacral arteries, 396 Internal iliac arteries, , 397 Glutaeal, obturator, pudic, &c 398 External iliac, 400 Femoral artery, ib. Profunda artery, 401 Circumflex arteries, ib. Popliteal artery, 402 Anterior tibial artery, 403 Posterior tibial, ib. Peronseal arteries 404 VENOUS SYSTEM, 405 Veins of the head, ib. External jugular vein, 406 Internal jugular vein, ib. Veins of the arm, ib. VensB innominatse, 407 Vena cava superior, ib. Vena azygos, ib. Veins of the leg, 408 Iliac veins, ib. 2 XIV CONTENTS. PAGE. Vena cava inferior 409 Vena port, ib. Haemorrhoidal, mesenteric, and splenic veins, ib. LYMPHATIC SYSTEM, 410 Thoracic duct, 411 Receptaculura chyli, ib. Structure of coats in arteries, veins, and lymphatics, 412 Foetal circulation, 413 Umbilical vein, ib. Ductus venosus, ib. Ductus arteriosus, ib. Thymus gland, 414 PART IV. OF THE BONES. The vertebrae,... 415 Sternum, 423 Ribs, 425 Thorax, , 427 Sacrum, 428 Ossa coccygis, 429 Ossa innominata, 430 Ilium, ib. Ischium, 431 Pubis, 432 Acetabulum, ib. Pelvis, 433 Head, 436 Frontal bone, ib. Parietal, 439 Occipital, 440 Temporal, 441 ./Ethmoid, 444 Sphenoid, ; 446 Sutures, 449 Skull in general, 451 Bones of the face, 452 Malar bone, 453 Superior maxillary bone, ib. Palate bone, 455 Inferior spongy or turbinated bone, 456 Os unguis or lachrymal bone, 457 Nasal bone, ib. Vomer, 458 Inferior maxillary bone, ib. Teeth, 460 CONTENTS. XV PAGE. Orbit, 461 Palatine region, 462 Temporal fossa, ib. Zygomatic fossa, ib. Pterygo-maxillary fo ssa, 463 Femur, ib. Patella or rotula, 466 Tibia, ib. Fibula, 468 Tarsal bones, 471 Metatarsal, 472 Phalanges, 473 Clavicle, 474 Scapula, 475 Humerus, 477 Ulna, 479 Radius, 480 Carpal bones, , 482 Metacarpal bones, 484 Phalanges, 485 Sesamoid bones, 486 PART V. OF THE JOINTS. General view of the joints, 489 Temporo-maxillary articulations, 491 Dislocations of the lower jaw, 493 Articulation of the occiput with the atlas, ib. Articulation of the occiput with the axis, 494 Articulation between the first and second vertebrae, 495 Common articulation of the vertebrae, 496 Inter. vertebral ligaments or fibro-cartilages, 497 Articulation between the pelvis and the spine, 499 Ligaments of the pelvis, 500 Articulations of the ribs, 501 LIGAMENTS OF THE SUPERIOR EXTREMITIES, 503 Sterno-clavicular articulation, 504 Scapulo-clavicular articulation , 505 Dislocations of the clavicle, ib. Ligaments of the scapula, 506 Humero-scapular or shoulder articulation, ib. Dislocations of the shoulder, 508 Humero-cubital articulation, or the elbow joint, 509 Radio-ulnar articulations, 510 Dislocations of the bones of the elbow joint, ib. Dislocations of the carpal extremities of the radius or ulna,.... 511 Xvi CONTENTS. PAGE. Radio-carpal articulation, or the wrist joint, 512 Articulations of the bones of the carpus, 513 Dislocations of the bones of the carpus, 515 Articulation between the carpus and metacarpus, ib. Dislocations of the metacarpal bones from the carpus, ib. Articulation between the metacarpus and the phalanges, 516 Dislocation of the thumb, ib. LIGAMENTS OF THE INFERIOR EXTREMITIES, 517 Ilio-femoral articulation, or the hip joint, ib. Dislocations of the hip, , 519 Femoro-tibial articulation, or the knee joint, , 52 1 Dislocations of the patella and knee, 526 Superior tibio-fibular articulation, * 527 Dislocation of the tibio-fibular articulation, 528 Inferior tibio-fibular articulation, ib. Articulation of the ankle, ib. Dislocations, &c. of the ankle, 530 Articulations of the bones of the tarsus, 531 Articulations between the tarsus and meta-tarsus, &c ib. APPENDIX. Direction for making dried preparations of arteries, 535 Laennec's division of the regions of the thorax, 539 Directions for opening the head, thorax, and abdomen, 540 THE DUBLIN DISSECTOR CHAPTER I. DISSECTION OF THE EXTERNAL PARTS OF THE FACE AND HEAD, - SECTION I. EXTERNAL PARTS OF THE HEAD. THE integuments covering the cranium are firm and dense, although when felt they give the sensation of being thin : the cuticle is delicate, but the cutis is very thick, and fur- nished with many sebaceous follicles ; the subjacent cel- lular membrane contains granulated fat, and the bulbs of the hairs, which afterwards perforate the skin in an oblique direction. The cellular tissue is condensed, having some- what a ligamentous structure, it adheres so intimately to the subjacent muscular and tendinous expansion, that the inexperienced student may find some difficulty in exposing the surface of the latter. Make an incision through the integuments along the median line, from the tuberosity of the occipital bone, as far forwards as the lower part of the forehead, from each extremity of this, make a transverse incision about three inches long ; let the posterior one be parallel to the superior transverse ridge of the occipital bone, and the anterior one parallel, and about half an inch superior to the eyebrow ; cautiously dissect off the integu- ments from the subjacent muscular and tendinous expan- sion, which is the occipito-frontalis. This muscle, like most of the superficial muscles of the face, is closely at- tached to the skin, which circumstance, added to the pale- ness and smallness of their fibres, renders their dissection somewhat difficult and tedious. Most of the superficial 2 DUBLIN DISSECTOR. muscles of the head and face, during life, assist some of the organs of sense, and contribute to produce certain changes in the countenance, indicative of character or passion, and expressive of many diseases, tetanus, perito- nitis, &c. In point of function, they may be considered as belonging to the class of mixed muscles, that is, they are in part voluntary and in part involuntary : with the exception of the aponeurosis of the occipito-frontalis, the tendon of the orbicularis palpebrarum, and that of the corrugator supercilii, there is no perfect tendinous struc- ture in the other muscles of this class. The superficial muscles of the head are divided into those of the cranium and face. Those of the cranium are the occipito-frontalis, and the three common muscles of the ear, to these some add the corrugatores superciliorum ; these, however, I prefer placing among the muscles of the face. [The following arrangement will give a comprehensive view of the muscles of the head and face, classed according to the part upon which they particularly act. There are six classes, including thirty, six pair of muscles, and two single muscles as follows : FIRST CLASS, ONE MUSCLE. Occipito Frontalis. Vide p. 4. This by its palpebral insertion becomes a muscle of the eye, and by its nasal process, a muscle of the nose ; it acts upon the scalp, eyebrow, lid, and nose. SECOND CLASS, ELEVEN MUSCLES. These are the muscles of the ear, and are arranged in three groups, the first of three muscles moves the external ear, upon the head ; the second of five muscles, moves the cartilages of the external ear, up. on themselves : the third of three muscles moves the bones of the internal ear so as to render the membrana tympani, lax or tense. First Group, three Muscles. Superior Auris, or Attollens. Vide p. 6. Anterior Auris, or Attrahens, ) -y , _ Posterior Auris, orRetrahens, \ v ' ae P- ' Second Group, five Muscles. Tragicus, ") Anti Tragicus, Helicis Major, V Vide p. 355. Helicis Minor, Transversalis Auris, J Third Group, three Muscles. S taped ius, } Tensor Tympani, > Vide p. 355. Laxator Tympani, ) DUBLIN DISSECTOR. 3 THIRD CLASS, ELEVEN MUSCLES, Including the occipito-frontalis. These are the muscles of the eye, and are found in two groups, the one of five muscles, acting upon the appendages of the eye, the other of six muscles, acting upon the ball of the eye. First Group, fine Muscles. Occipito-frontalis., its palpebral insertion, Vide p. 14. Corrugator Supejrcilii. " " 16. Levator Palpebra; Superioris, " " 361. Orbicularis Palpebrarum, " " 8. Tensor Tarsi, " " 10. These muscles are .all exterior to the orbit except the Levator Pal- pebroe Superioris which is within. Second Group, six Muscles, all within the orbit. Superior Rectus, or Levator oculi, Inferior Bectus, or Depressor oculi, Internal Rectus, or Adductor oculi, External Rectus, or Abductor oculi, Obliquus Superior, Obliquus Inferior, FOURTH CLASS, FOUR MUSCLES. These are the muscles which act upon the nose, and they .are ar- ranged in two groups, the one of two muscles proper to the nose ; the other also of two muscles common to the nose .and upper lip. First Group, two Muscles, proper to the nose. Pyramidalis Nasi, a process of the occipito-frontalis, Compressor Nasi, Second Group, two Muscles, common to the nose and upper Lip. Levator Labii Superioris alaeque nasi, Vide p. 11. Depressor Labii Superioris alaeque nasi, " " J2. FIFTH CLASS, TEN MUSCLES.. These are the muscles which act upon the different parts of the mouth and are arranged in four groups, the first group includes but one muscle, which surrounds the whole mouth ; the second embraces two muscles, which act upon the upper lip (already enumerated, as common to it, and the nose) the third includes two muscles, which act upon the lower lip, and the fourth five muscles, which act upon the angle of the mouth. First Group, one muscle a single muscle. Orbicularis Oris Vide p. 13. Second Group, two Muscles, common to the upper lip and nose. Levator Labii Superioris alasque nasi, Vide p. 11. Depressor Labii Superioris aleeque nasi, " " 12. Third Group, two muscles. Levator Labii Inferioris, Vide p. 13. Depressor Labii Inferioris, " " 12. 4 DUBLIN DISSECTOR. Fourth Group, five Muscles. Levator Anguli Oris, Vide p. 12. Depressor Anguli Oris, " " 12. Zygomaticus Major, * "11. Zygomaticus Minor, " " 11. Buccinator, " " 13. In the case of the eyelids, the contraction of the orbiculans and consequent disfiguration is guarded against, by the cartilaginous tarsi placed along the adjoining margins of the lids ; but in the case of the mouth, the contraction of the orbicularis and consequent disfiguration, is guarded against by the numerous muscles just men- tioned, and which are inserted extensively into the lips and their commissures or angles ; this is demonstrated by the distortion of the mouth, in those cases where one side of the face is paralysed. SIXTH CLASS, FOUR MUSCLES. These muscles act upon the inferior maxillary bone, in raising the jaw and in mastication ; they are variously situated, one being on the side of the face, one on the side of the head, and the other two beneath the base of the cranium, and within the inferior maxilla. They constitute one group. Masseter, Vide p. 19. Tempor&lis, " " 21. Pterygoideus Intern us, " " 22. Pterygoideus Externus, " " 23. Of all the muscles above enumerated, the orbicularis oris and the occipito-frontalis, are the only two, usually described as single muscles, all the rest being in pairs. The last mentioned group of muscles are those which are concerned in dislocations of the lower jaw.] OCCIHTG-FKONTAMS as the only muscle which properly belongs to the scalp ; it is a thin, broad, digastric, or rather quadriceps muscle, fleshy at each extremity, apo- neurotic in the centre. It arises on each side by tendinous and fleshy fibres, from the two external thirds of the su- perior transverse ridge of the occipital bone, and from the external and posterior part of the mastoid process ; the fibres on each side ascend from behind forwards and from without inwards, and soon terminate in one thin and broad tendon, which extends over the upper and lateral parts of the cranium. This epicranial aponeurosis having arrived opposite the coronal suture, ends in two fleshy portions, broader and thicker than the posterior extremi- ties of the muscle; these anterior portions, which are thicker externally than internally, descend over the front- al bone, and are inserted, fleshy on each side, into the inte- gument of the eyebrow, mixing with the fibres of the cor- rugator supercilii and orbicularis palpebrarum muscles : DISSECTOR. 5 a small fleshy slip is often continued down along the nasal bones, and is attached to the angular process of the os frontis, and inferiorly to the nasal bones or cartilages : this slip is described by some as a distinct muscle, under the name of pyramidalis nasi, or fronto-nasalis. Use. The occipi- to-frontalis muscle can raise the eyebrows and integument of the forehead in transverse wrinkles, draw the eyebrows a little outwards, and make tense the skin of the upper eyelids, and thus expose the eyeball, as in staring, it can also pull the scalp backwards ; but if the eyebrows be de- pressed and fixed, this muscle can then (particularly in some persons) draw the scalp downwards and forwards. This muscle is very closely connected to the scalp, par- ticularly in front, but loosely to the cranium, it can thus move easily on the latter, carrying with it the former, which it also serves to support in apposition with the cra- nium, so as to prevent the skin slipping or yielding when any weight is pressed against the head. Its origin is connected with the sterno-mastoid, the tra- pezius, and splenius muscles, and its insertion with those of the eyebrows. Some describe the occipito-frontalis, not as one, but as four distinct muscles, two on each side, under the names of the occipital and frontal muscles of each side, and consider the cranial aponeurosis as their common insertion. Several vessels and nerves perforate this muscle, and ramify on its surface and in the integu- ment, viz. anteriorly the supra-orbital branches of the ophthalmic nerve and artery ; laterally, the temporal and posterior auris arteries with branches of the portio dura and inferior maxillary nerves, and posteriorly, the occipi- tal arteries spread their branches upwards and forwards, accompanied by the occipital nerves, branches of the cer- vical plexus. It covers from behind forwards, the occipi- tal, temporal, parietal, and frontal bones, also the upper portion of each temporal aponeurosis, the corrugator su- percilii muscle, and the supra-orbital nerves and vessels. The cranial or epicranial aponeurosis is composed of ten- dinous fibres which are distinct, glistening, and parallel behind, but anteriorly become weak, greyish, and inter- laced like cellular tissue, and frequently deficient in spots. The integuments in this region are highly organized, being supplied with numerous nerves and vessels, these are derived from different and distant sources, and are chiefly destined to nourish the hair bulbs in the cellular tissue ; in the line of the sutures they have frequent in- osculations with the vessels of the diploe, and of the dura mater. This high organization of the scalp is not only of anatomical but of practical importance, as it serves to ex- 6 DUBLIN DISSECTOR. plain many of the pathological phsenomena which are of ordinary occurrence in this region ; thus, it is frequently the seat of encysted tumours, horny growths, &c., these appear to arise in the sebaceous follicles, the ducts of which have become obstructed from irritation or injury ; a vitiated secretion then accumulates in the sac, which some- times becomes circularly enlarged, and at others the con- tents slowly escaping from the ducts, and hardening, as- sume horny and various other appearances. The scalp is a common seat of erysipelas, both idiopathic and sympto- matic. Injuries of it are of very frequent occurrence, and are more serious than those of the same extent in other situations. Incised wounds bleed more freely ; punctured wounds are very frequently followed by high inflamma- tory symptoms, local and general, in consequence of mat- ter being confined under the tense epicranial aponeurosis, which, in such cases, will require free division. The compact density of the cellular tissue explains the hard rim which surrounds the ecchymosis, the effect of injury, [and also explains the deceptive appearance of fracture and depres- sion of the bone which is sometimes presented when the injury is in fact merely a contusion followed by the effusion of blood. As above stated the scalp is very abundantly supplied with blood which is de- rived principally from the frontal branches of the internal carotid, and the temporal, posterior auricular, and occipital branches of the ex- ternal carotid ; these anastomose very freely with each other, on the same side, and also very freely across the top of the head with the same branches of the opposite side, and hence the severe and extensive operation which is necessary for aneurism by anastomosis of the scalp, which operation consists in circumscribing the tumor, sometimes even after the common carotid artery of the affected side has been ligatured. Foran extensive aneurism of this kind, both common carotid arteries were ligatured with perfect success, by Prof. Mussey, at that time of Dartmouth College. The scalp is also the seat of encephaloid disease and nsevi materni.J In the foetus the scalp is very thin, and the aponeurosis is loosely attached to the cranium by reticular membrane; this, and not the subcutaneous cellular tissue is the seat of those large ecchymoses eo commonly seen after parturi- tion, and which in general are quickly removed by the absorbent system. The common muscles of the ear are three in number, viz. superior, anterior, and posterior auris : SUPERIOR AURIS, or ATTOLLENS AUREM, is a small, thin, triangular muscle, situated on the temple, and above the ear, arising broad and tendinous from the cranial aponeu- rosis, where it covers the temporal fascia on the side of the cranium, just above the external ear ; the fibres de- scend converging, become fleshy, and are inserted into the DUBLIN DISSECTOR. 7 upper and interior part of the cartilage of the ear : use, to raise the cartilage, and deepen the meatus of the ear, also to make tense the epicranial fascia. This muscle is be- tween the skin and temporal fascia, its anterior edge is confounded with the following muscle. ANTERIOR AURIS, or ATTRAHENS AUREM, is connected with the last, is of the same form, but smaller, and often indistinct ; it arises from the posterior part of the zygoma- tic process, and from the cranial aponeurosis, passes back- wards and downwards, and is inserted into the anterior part of the helix ; use, to draw the external ear forwards and upwards. This muscle is superficial, and lies on the temporal fascia, vessels, and nerves, its lower edge is lost in the cellular tissue. POSTERIOR AURIS, or RETRAHENS AUREM, often consists of two or three distinct fasiculi, it is the strongest of these auricular muscles ; it has no connection to the epicranial fascia, but arises from the mastoid process above the ster- no-mastoid muscle, passes forwards, and is inserted into the back part of the concha ; use, to enlarge the meatus of the ear and direct it backwards. This muscle is covered only by the skin, it lies upon the temporal bone. In addition to these muscles, which move the external ear, there are several small muscles attached to different parts of the cartilages, which serve to alter their form, and expand their cavities ; these muscles, as also those in the tympanum, shall be described hereafter in the dissec- tion of the organ of hearing.* SECTION II. DISSECTION OF THE EXTERNAL PARTS OF THE FACE. The muscles of the face require careful dissection ; they are delicate, and often very pale ; they may be classed into the superficial and deep : the former into those of the eyelids, nose, lips, and mouth ; the latter into those of the lower jaw and palate. Make an incision around the base of the orbit, through the skin, which is here very *Previous to, or immediately after dissecting the muscles of the face, the student should examine the brain, the description of which organ will be found at the head of that of the nervous system. 8 DUBLIN DISSECTOR. fine, and closely adhering to the fibres of the orbicularis muscle; next make a perpendicular incision along the middle line of the nose, to the centre of the upper lip, continue this in a semicircular manner round the angle of the mouth to the middle of the lower lip, and thence to the chin, and lastly from the chin to the angle of the jaw ; reflect the integuments cautiously from the eyelids and side of the face, as far back as the ear, avoiding the slender muscular fibres which adhere to the skin, and the vessels and nerves which will be exposed in this dissection. The superficial muscles of the face may be considered as thirty-three in number, that is sixteen pair and one azygos, and are arranged as follows. Three pair belong to the palpebrcc., viz. orbicularis pal- pebrarum, tensor tarsi, and corrugator supercilii, (the le- vator palpebrse is deep seated in the orbit, and is arranged among the muscles of that region.) Four pair belong to the nose, viz. pyramidalis nasi, leva- tor labii superioris alseque nasi, compressor and depres- sor naris. Three pair belong to the upper lip, viz. levator labii superioris, levator anguli oris, and depressor labii superi- oris. Three pair belong to the lower lip, viz. depressor anguli oris, depressor labii inferioris, and levator labii inferioris. Three pair belong to the mouth, viz. zygomaticus major, minor, and buccinator, and one azygos, the orbicularis oris ; writers vary this arrangement, but no material dif- ference exists. ORBICULARIS PALPEBRARUM, broad and thin, somewhat oval, in some subjects very pale and indistinct, in others strong and well marked, it surrounds the base of the orbit, and occupies a great portion of the face ; it arises by sev- eral fleshy fibres from the internal angular process of the os frontis, and from the upper edge of a small horizontal tendon, (which tendon, TENDO OCULI, or TENDO PALPEBRARUM, [or internal Palpebral Ligament,] which is nearly one half of an inch in length, is inserted internally into the upper end of the nasal process of the superior maxillary bone, thence it passes outwards and backwards to the internal commissure of the eyelids, where it forks into two slips which enclose the caruncula lachrymalis, and are then inserted each, into the tarsal cartilage, and the lachrymal duct ;) the fleshy fibres then proceed in curves, upwards and outwards, along the upper edge of the orbit, the eye- lid, and tarsal cartilage, as far as the temple and external commissure of the eyelids ; thence the fibres curve in a similar manner along the inferior eyelid and edge of the DUBLIX DISSECTOR. 9 orbit to the internal canthus, where the fibres are inserted into the nasal process of the superior maxilla, and into the inferior edge of the horizontal tendon. Use, to close the eyelids, chiefly by depressing the superior, the levator muscle of which it directly opposes, it also serves to press the tears inwards towards the puncta lachrymalia ; the superior and external fibres can depress the eyebrow, and thus oppose the occipito-frontalis and shade the eye ; the inferior fibres can raise the cheek, raise and draw the low- er eyelid inwards, and compress the lachrymal sac, which they cover. In sleep it is relaxed, and the eye is covered chiefly by the descent of the upper palpebra, its elevator being also relaxed: when awake its contraction covers the globe, not only by bringing down the upper, but also by elevating the lower eyelid, hence the "equator oculi," the line formed by the approximated tarsi, is lower during real than in feigned sleep ; in the former, also, the cornea is seldom entirely covered, as it always is in the latter. This muscle is covered by aad adheres to the skin : su- periorly it intermixes with the oocipito-frontalis, and covers the corrugator supeircilii, the frontal vessels and nerves, the tarsal cartilage , when they con- tract. BUCCINATOR, is broad, thin, and somewhat square, situated between the two alveolar arches, it forms the inner side of the cheek, and the lateral boundary of the mouth, and lies close to the mucous membrane of the latter ; arises poste- riorly from the two last alveoli of the superior maxilla, as far back as the pterygoid process, from the external sur- face of the posterior alveoli of the lower maxilla, as far back as the coronoid process, and forms a strong aponew- rosis, named the intermaxillary ligament, which extends from the extremity of the internal pterygoid plate to the root of the coronoid process, and which affords attachment 2 14 DUBLIN DISSECTOR, to the superior constrictor of the pharynx posteriorly, and to the buccinator anteriorly. From these three origins the fibres pass horizontally forwards, converging a little, and are inserted into the commissure of the lips, where they in- termix with those of the orbicularis, and of the other mus- cles at the angle of the mouth. Use, to press the cheek against the teeth, so as to bruise and push the food between them, and to diminish the cavity of the mouth, as in masti- cation and deglutition ; it is also much engaged in the arti- culation of certain expressions, as well as in filling wind instruments ; it can also retract the commissure of the lips. The buccinator is covered by a considerable quantity of fat, which separates it from the coronoid process of the lower maxilla, and from the insertion of the temporal mus- cle, this fat often extends in the form of large, soft, round masses beneath the masseter muscle ; it is also covered by the zygomatic, the depressor anguli oris and platysma muscles, and by the facial vessels ; several branches of the facial artery and vein, and of the seventh and fifth pairs of nerves, ramify on its surface ; it lies on the mucous mem- brane, and on a number of small round mucous glands called buccal ; it is perforated near its superior posterior third by the duct of the parotid gland, opposite the third superior molar tooth. The deep muscles of the face, which are connected with the lower maxilla, and which are employed in the process of mastication, are the masseter, temporal, internal, and external pterygoid of each side : previous to dissecting these, the student should examine the situation and con- nexions of the parotid gland, the chief of the salivary glands. There are six salivary glands, three on each side, the parotid, submaxillary, and sublingual. The salivary glands, together with the lachrymal, mam- mary, and pancreas, are commonly called conglomerate glands, in contradistinction to the absorbent, or lymphat- ic, or conglobate glands; this term, however, is by no means distinct or definite, for other glands, viz. the liver and kidney, are equally conglomerate, though not so ob- viously such. The general arrangement of the glandular system we propose, is into two orders, the Absorbent and Secreting ; the absorbent, or lymphatic, or conglobate, will be noticed hereafter : the secreting order may be divided into two classes, viz. the simple and the complex ; the simple are the numerous glands which are attached very general- ly to the mucous membranes ; the compound secreting or conglomerate glands, are the lachrymal, salivary, mam- mary, pancreas, liver, kidney, prostate, and testis. There is no evidence for considering the pinaeal, pituitory, thy- DUBLIN DISSECTOR. 15 roid, thymus, or supra-renal bodies, or the spleen and ovaries as true glands. [Here, as in most of the systems of anatomy tbe term gland is applied to two classes of organs which differ essentially in their structure, their relations, and their functions, viz. the glands proper and the lymphatic ganglia. If we examine the works on general anato- my, we shall find that the glandular tissue is defined as consisting of an assemblage of secreting organs, more or less globular in form, and having an excretory duct lined with mucous membrane, which terminates directly or indirectly upon the surface of the body : this being the case, it is evident that in the present state of our knowledge, the lymphatic or absorbent bodies cannot be brought under the head of glands ; it is therefore better to drop the term as applied to them, because it leads to error as to their functions, &c., and substitute the term ganglion, which is used by some writers. Accordingly, in revising this book the tenms ganglion and ganglia are substituted for gland and glands, whenever used as referring to the lymphatic bodies. The glands proper, as stated above, may be divided into simple and compound; and the compound may be again divided into conglobate and conglomerate : by conglobate we mean glands com- posed of an assemblage of glandular particles united in jnass by cellular tissue, and having a common and distinct sheath or .covering, as the liver : by conglomerate we mean an assemblage of small conglobate glands, united together by cellular tissue, and connected iby an indistinct covering of loose cellular substance, the whole organ presenting an uneven lobulated appearance, instead of being smooth, and the excretory ducts of each lobule terminating in a common duct, as the pancreas, &c.] The salivary glands, including the lachrymal, the mam- mary, and the pancreas, all correspond in certain charac.- ters, in which, also, they differ from other secreting glands : they are all symmetrical, except the pancreas, which however, is attached to the digestive organs, the chief ap- paratus of organic life, but one in which no symmetry is observed : they are of a pale grey colour, with a slight red- dish tint; the virgin mammary gland is almost white; they have no perfect capsule, except the mammary,, and that, though perfect, is very thin and loose : their form and size are not accurately defined, two or more being sometimes connected; they are very irregular in these respects ; their texture is loose, that is, they consist of grains which are but loosely connected by cellular tissue and vessels into small lobules, and these into larger lobes: the granules themselves are very firm and compact: they are all well supplied with nutrient vessels, the arteries ramify minutely before they enter them, which they do at all parts of their surface, and not at any particular fissures, as in the liver and kidney ; the transit of the carotid and facial ^arteries through the parotid and sub- 16 DUBLIN DISSECTOR. maxillary glands is not an exception to this statement : the veins in like manner escape at different parts, and enter the neighbouring vessels: their excretory ducts in some unite into one vessel, which proceeds to its destina- tion, but in others, as in the lachrymal, mammary, and sublingual, they continue separate to the surface. In no case is there any perfect reservoir to delay or retain the secretion, as in the case of the liver and -the gall bladder, the kidney and the vesica ; the lachrymal sac cannot be considered as such : they are largely supplied with nerves, and, except the filaments of the sympathetic, which ac- company the vessels, these are derived from the spinal and cerebral system ; the pancreas is an exception to this rule: not only cellular tissue in abundance, but even adipose enter into their composition : they are in close connexion with the lymphatic or absorbent system, nu- merous lymphatic vessels pervade them, and lymphatic ganglia are in their close vicinity, and 'occasionally even imbedded in their substance. In many -of these characters, the salivary glands form a remarkable contrast with the other complex secreting glands, which "will more fully ap- pear when the latter come under our notice. All the se- creting glands, simple as well as compound, are subject to many diseases ; these will be noticed in the account of the individual glands. The PAROTID GLAND is the largest of these conglomerate glands, it derives its name from its proximity to the ear ; it is exposed by dissecting off the integuments and some fibres of the platysma, also a dense fascia which covers and adheres to it ; this fascia is continued from that of the neck, spreads over the gland, is closely connected to the cartilaginous part of the meatus auditorius, and sends nu- merous processes into the gland in every direction, serving to separate its lobules, and to conduct the different vessels through its substance. The parotid gland is not of any regular figure, by some it is considered pyramidal, the apex above, the base directed outwards and downwards ; by others, (the upper end being more developed,) an ir- regular square ; as such we shall consider it, and, of course, as presenting two surfaces, a superficial and a deep, and four margins, a superior, inferior, anterior, and posterior : it occupies, together with some other important parts, that deep excavation on the side of the face between the lower jaw and the auditory meatus, it also extends into the small region of the neck, named the posterior digastric space ; it is bounded above by the zygoma, below by a line drawn from the angle of the jaw to the mastoid process, posteri- orly by the meatus auditorius, the mastoid process, and DUBLIN DISSECTOR. 17 sterno-mastoid muscle, and anteriorly by the masseter muscle, the posterior third of which it overlaps. The ex- ternal surface is pale, flat, or slightly convex, in this re- spect, however, differing in different persons, as it also does in superficial extent ; probably the absence of a regular .capsule may in some measure account for this diversity ; the anterior and inferior margins are the least defined, are irregular in their extent, in some they considerably exceed the ordinary bounds ; the superior border is limited by the attachment of the fascia to the zygoma, and the posterior is resisted by the meatus of .the ear, and by the sterno- mastoid muscle. The connexions of the deep surface may be examined after the course of the excretory duct, and of the several vessels and nerves which pass through the gland, shall have been exposed. The Parotid or Steno's duct arises from its anterior superior border, and is formed by the union of numerous small vessels, which issue, each, from one of the granulations of the gland ; it passes forwards over the masseter muscle about an inch below the zygoma, parallel to a line drawn from the tube of the ear to midway be- tween the commissure of the lips and the root of the nose ; it winds round the anterior e4ge of the masseter, beneath the zygomatic muscles and through a quantity of soft adeps, pierces the buccinator, and opens through the mu- cous membrane of the mouth by a very small hole oppo- site the second or third superior molar tooth, about half an inch from the junction of the cheek with the gum. Be- tween the duct and the zygoma, a small, smooth, glandu- lar mass is frequently found ; it appears like a detached lobe of the parotid, it is named the soda parotidis ; from the lower and anterior part of this process, a small duct pro- ceeds, which after a short course unites with the duct of Steno ; in some this duct opens distinctly into the mouth. The transverse artery of the face, and several branches of the facial nerve, accompany this vessel, and in general the artery is superior to it, while the nerves wind around it. This duct appears much larger than its calibre really is ; it is formed of two coats, the external, white, fibrous, and dense, commences beyond the anterior edge of the gland, and ends at the buccinator muscle ; and the internal, a fine, delicate, mucous membrane, is continuous with that lining the mouth : the canal is larger at the commencement and outside the buccinator than in the intervening space, or at the orifice in the mouth. The parts which pass through this gland are the exter- nal carotid artery and several of its branches, with their accompanying veins, and branches of the inferior maxil- 2* 18 DUBLIN DISSECTOR. lary and cervical nerves, also the plexus of the portio dura, or facial nerve. The first or most superficial of these parts is the ascendens colli nerve, or the superficialis colli or auricularis, it enters the gland near its lower bor- der, and is lost chiefly in communicating with the portio dura ; this last-named nerve escapes from the cranium by the stylo-mastoid foramen, enters the gland at its posterior inferior part, passes forwards and upwards through it, and forms in its substance the remarkable plexus, parotida an, or pes anserina, which crosses superficial to the external car- otid artery, and then separates into its two great divisions, the superior and inferior ; a small portion of the gland in- tervenes between it and the vessels. The branch of the inferior maxillary nerve, which traverses the gland is the temporo-auricular,' which will be found between the neck of the lower jaw and the meatus auditorius, about half an inch above, but much .deeper than the portio dura, with which it communicates, and for which it is sometimes mistaken. The external carotid artery will be found to enter the low- er border of the gland, near its deep surface,; as it ascends it is crossed by the portio dura, and becomes much more superficial, its posterior auricular branch borders the low- er and back part of the gland, the temporal ascends through it, the internal maxillary is deeply imbedded in it in its course forwards and inwards, the transverse facial artery also traverses it in a direction forwards, and it also gives off numerous branches to the granules of the gland and to the ear. The veins corresponding to these arteries also pass through this organ ; the temporal and internal max- illary, by their confluence, which i-s superficial to the ex- ternal carotid artery, and very rarely to the portio dura also, forms the external jugular vein, which descends through the gland, and becomes then superficial in the neck. Sev- eral lymphatic vessels .and ganglia are connected with the parotid, particularly to its inferior border ; generally one or two small ganglia .may be found imbedded in its sub- stance, in front of the meatus auditorius, just where its cartilage is deficient. Now divide the parotid duct, raise off the gland from the masseter muscle, and from .the ramus of the jaw, and observe its 'several deep-seated connexions. The deep or posterior surface of the gland is very ir- regular, it covers the .posterior third of the masseter, also the ramus of the jaw, behind which it sinks, and fills the deep excavation between this bone and the ear, envelops the.styloid process of the temporal bone and the muscles which arise from it, and it touches the internal carotid DUBLIN DISSECTOR. 19 artery, jugular vein, and the large nerves connected with these vessels ; it also fills the posterior part of the glenoid cavity in the temporal bone, and adheres to the capsular ligament of the maxilla, inferiorly it is wedged in between the internal pterygoid, digastric, and styloid muscles. The styloid process is in some cases so involved in it as to appear to divide the gland into a superficial and a deep lobe, the latter will then be deeper than this process and in close connexion with the great cervical nerves and ves- sels : a portion of the gland will also be found to accom- pany the internal maxillary artery between the ramus of the jaw and its internal lateral ligament ; this touches the inferior maxillary nerve, and in many instances extends into the fatty space between the two pterygoid muscles, where it swells out to a considerable size, so as to appear like a distinct lobe connected to the body of the gland by a narrow neck. The parotid gland is composed of numerous small gran- ulations, united together by cellular tissue, by branches of blood-vessels and nerves, and by the small roots of its ex- cretory duct. This gland is subject to several MORBID changes, viz. inflammation, or cynanche parotidsea, or parotitis, or mumps; abscess; hypertrophy, or scirrhus induration, which sometimes requires extirpation ; scirr- hus, ending in cancer ^ fistula, the effect of abscess or wound of the .gland or duot ; atrophy, or absorption, this latter condition is usually caused by tumors, lymphatic or encysted, these by degrees come to occupy the position of the gland and cause its absorption. -Such tumors simulate the enlarged parotid, though essentially different, they ad- mit of more easy extirpation as they are usually surround- ed by a capsule, and are nat traversed by the adjacent nerves and vessels. [This gland is also the seat of encephaloid disease, of melanosis, and of fatty degeneration ; salivary calculi also occur sometimes in its ducts : but the mumps is the disease to which it is most subject. This is an infectious disease, usually occuring but once, attacking young persons and on both sides, and not (infrequently presenting a metastasis in the male to the testicle, and in the female to the breast : several cases are reported of the successful extirpation of this organ, in this country, by Drs. Bush, McClellan and Parker.] Next clean the masseter muscle. and 'the temporal apo- neurosis. MASSETER: the greater part of this muscle is superficial, it is thick and strong, covers Scalenus Medius, > Vide p. 65. Scalenus Posticus, j Fifth Group, three pair of Muscles. Stylo-Hyoideus, Vide p. 43. Stylo-Glossus, ) v , , ,. Stylo-Pharyngeus, \ V( These are the styloid muscles extending from the styioid process of the temporal bone, to the os hyoides, tongue, and pharynx, they are situated in the supra-hyoideal space, and are muscles of deglutition, being antagonists of the second group, and congeners of the third. Sixth group, four pair of Muscles. Lingualis, Vide p. 43. Superficial Lingual Muscle. 1 Transverse Lingual Muscle, > Vide p. 50. Vertical Lingual Muscle, ) These are the proper muscles of the tongue, being situated entirely in that organ, and forming a large part of its substance. They are of course in the supra-hyoideal region. Seventh Group, three pair of Muscles. Constrictor Pharyngis Inferior, Vide p. 51. Constrictor Pharyngis, Medius, ) v -j ,.9 Constrictor Pharyngis Superior, { These muscles are situated on the back and sides of the pharynx, they are muscles of deglutition, and are partly above, partly below, the level of the es hyoides. Eighth Group, four pair ; and a single Muscle. Leva'tor Palati, ) Tensor Palati, or Circumflexus, r Palato-Glossus, or Constrictor Isthmi Faucium, > Vide p. 55. Palato-Pharyngeus, Motor, or Azygos Uvulee, a single Muscle, J These muscles are situated upon the soft palate, and are above the os hyoides, they act upon the velum, in such manner as to cut off the openings of the posterior nares, from the pharynx in deglutition, so as to prevent the food or liquids from being thrown up into the nares ; or on the other hand, they cut off the mouth from the pharynx, so DUBLIN DISSECTOR. 31 that fluids or gases, may be thrown up into the nostrils, and pass out through the anterior nares. Ninth Group, seven pairs ; and a single Muscle. Crico.Thyroideus, Vide p. 61. Crico-Arytenoideus Posticus, M " 62. Crico-Arytenoideus Lateralis, ') u 44 ... Thyreo-Arytenoideus, ^ Arytenoideus Obliquus, "| Arytenoideus Transversus, a single Muscle, I Tr . , Aryteno-Epiglottideus, ' Vlde ?' 62 ' Thyreo-Epiglottideus, These are the proper muscles of the larynx, they are below the OH hyoides, and are situated parily externally, partly internally, in refer- ence to the circumference of the thyroid cartilage ; they act upon the cartilages of the larynx in such manner, as to enlarge or diminish the area of the rima glottidis, and relax or make tense the chords voca- les, hence the}' are the muscles of the voice.] DISSECTION OF THE MUSCLES. RAISE the shoulders of the subject by blocks placed beneath them, so as to make tense the muscles in this region ; divide the integuments, which in this region are thin and delicate, near to, and in a line with the clavicle, also along the side of the jaw from the chin to the mastoid process : connect these incisions by another made in a perpendicular direction, in the middle line from the chin to the sternum; dissect off the integuments from before backwards, in an oblique direction, from the chin towards the clavicle; this should be done cautiously, to avoid injuring the platysma or fascia ; in the child and in the female there is generally more subcutaneous fat than in the male subject. The platysma myoides will be now fully exposed, and the sterno-mastoid and hyoid muscles partially so ; in the middle line of the neck a chain of projections may be observed, which can also be felt during life, viz. a little below, but at some distance behind the chin, is the body of the os hyoides ; inferior to this is the angle of the thyroid cartilage ; next is the cri- coid below which the commencement of the trachea may be felt, on the forepart of which the soft swelling of the thyroid body can be discerned ; and lastly, the continua- tion of the trachea descending into the chest. The mus- cles on the anterior part of the neck are very numerous, they are concerned in several functions and execute dif- ferent motions ; some act as the ordinary muscles of lo- comotion, others are -occasionally engaged in deglutition, and in respiration, also in the exercise of voice and speech. They are symmetrical, or similar on each side of the mid- dle line ; they are twenty-one pair in number, and may be arranged for the convenience of dissection into three layers, 02 DUBLIN DISSECTOR. a superficial, middle, and deep ; the superficial consists of two pair, the platysma myoides and sterno-cleido mastoid ; the middle may be divided into two orders, the inferior and superior ; the inferior are three in number, viz. sterno-hyoid, thyreo-hyoid,and omo-hyoid ; the superior are nine in num- ber, viz. digastric, mylo-hyoid, genio-hyoid ; three styloid muscles, hyo-glossus, genio-hyo-glossus, and lingualis mus- cles ; the deep layer consists of seven pair, viz. longus colli, rectus capitis anticus, major and minor, rectus lateralis, and three scaleni ; this arrangement excludes the muscles of the palate, pharnx, and larynx. I^LATVSJVTJUMYOIDES, or latissimus colli, is a .thin and pale cutaneous muscle, in many subjects weak, and even indis- tinct, is situated on the forepart and side of the neck, ex- tending from the thorax to the face ; its figure is somewhat square, being a little longer than it is broad, and narrower in the centre than at either end; it arises by many fine fleshy fibres from the cellular membrane, covering the up- per part of the deltoid and pectoral muscles, a few also adhere to the clavicle ; the fibres ascend obliquely inwards, at first loosely, afterwards closely connected to each other, and form a broad thin muscle, covering the side of the neck, inserted, first, into the skin and cellular tissue on the chin, decussating there with fibres from the opposite side ; second, into the fascia along the side of the lower jaw, a few only into the bone ; some fibres may be traced high on the face, and seen to join the depressor anguli oris, the zygomatic and orbicularis palpebrarum muscles; and third, into the fascia, which covers the parotid, and which adheres to the meatus auditorius. Use, to depress the angle of the lips and the lower jaw, but if the mouth be closed it may elevate the integuments of the neck ; it also serves to compress and support the several muscles, glands, and vessels in this region. The platysma is covered only by the skin [and anterior lamina of the superficial fascia;] it partly 'conceals the clavicle and the deltoid and pectoral muscles, the sterno-mastoid, hyoid, and thyroid muscles; also the digastric and stylo-hyoid, the sub-maxillary gland, the lower part of the parotid, the side of the jaw and some of the muscles of the face ; also, in part, the external, ju- gular vein : this vein commences in the parotid gland, de- scends obliquely outwards over the sterno-mastoid muscle, where it lies very superficial and then sinks behind the clavicle, and joins the subdavian vein or some of its branches. The upper portion of the external jugular vein is accompanied by a large nerve, which lies to its outer side, superficialis colli, a branch of the cervical plexus as- cending to the parotid gland and external ear. This vein DUBLIN DISSECTOR. 33 in its course down the neck receives several cutaneous veins, and frequently communicates with the internal ju- gular : it presents great varieties in its size and course, and is sometimes even wanting. Superficial veins may also in general be marked descending along the anterior part of the neck ; they arise about the os hyoides and upper part of the thyroid body, and descend beneath some fibres of the platysma along the anterior edge of the mastoid mus- cle, and end in the internal or external jugular, or in the vena? innominate. [Variety. This muscle is sometimes though rarely found thick and round, and inserted into the occiput instead of being distributed upon the face.] The fibres of the platysma are closely connected to a layer of condensed cellular tissue, which in some sub- jects* is very strong, and in some situations aponeurotic ; this is the superficial cervical fascia ,* this fascia extends over the anterior and lateral parts of the neck ; is con- tinued down over the forepart of the thorax, where it becomes cellular and adipose ; ascends to the jaw, to which it is attached; expands over the parotid gland and adheres to the cartilage of the ear ; dn this situation its strength is greatly increased : towards the lateral and pos- terior parts of the neck it becomes weak like cellular mem- brane. From the posterior or deep surface of this fascia a lamina of membrane is derived, which passes behind the sterno-mastoid muscle : this is the deep cervical fascia, whose connexions are important, and may be examined in this stage of the dissection. If the superficial lamina bo di- vided along the median line of the sterno-mastoid muscle, this deep fascia will be seen to be continuous with or pro- duced from the superficial, and to pass behind the anterior border to the posterior surface of that muscle, so that the latter may be considered -as enclosed between these fasciae : at the lower part of the neck it is strong, and adheres to the inter-clavicular ligament and posterior edge of the sternum and clavicles. Some loose fatty substance is here interposed between it and the superficial fascia: as the deep fascia extends upwards, it covers and adheres to the sheath of the cervical vessels, and arriving at the space between the trapezius and mastoid muscles, it becomes weak and cellular, inferiority accompanying the great ves- sels beneath the clavicle, and superiorly lost on the branches of the cervical plexus of nerves ; at the superior and lat- eral parts of the neck it sinks deep, behind the angle of the jaw, to which it adheres, and is connected to the styloid process of the temporal bone, and to the stylo-maxillary ligament ; absorbent ganglia, the lower part of the parot- 34 DUBLIN DISSECTOR. id, and much cellular membrane here lie between these two fascse. In this situation collections of matter often form, the result of cynanche parotidyea, or of inflammation of some of the lymphatic ganglia: such collections are productive of great inconvenience, causing such swelling and tension as to interfere with the motions of the jaw, and with the act of deglutition. The cervical fasciae bind down the muscles and support the vessels and glands in this re- gion ; at the lower part of the neck they serve to protect the trachea and the upper part of the thorax from the pressure of the atmosphere during inspiration. Dissect off the platysma and superficial fascia, and examine the subjacent muscles, the second pair of the first order, ^yERNo-CLEiDo MASToiDEus, long and flat, placed at the anterior and lateral part of the neck, arises by a strong flat tendon with fleshy fibres posterior to it, from the upper and anterior part of the first bone of the sternum, also by short aponeurotic and fleshy fibres from the upper and an- terior edge of the sternal third, sometimes half of the clavicle ; a small triangular space separates these two or- igins, through which small vessels and some cellular mem- brane pass : this space corresponds to the sterno-clavicu- lar articulation. The sternal and longer portion of this muscle ascends obliquely backwards and outwards, and overlaps the clav- icular, which ascends vertically; about the middle of the neck they are intimately joined, and are inserted by a thin, broad aponeurosis into the upper part of the mastoid pro- cess, and into the external third of the superior transverse ridge of the occipital bone. Use, the sternal portion can rotate the head so as to turn the face towards the opposite side : the clavicular can bend the head and neck to its own side, so as to approximate the ear and shoulder ; and if the two portions of the muscle on each side act together, they will move the head downwards and forwards, but if the muscles on the back of the neck be in action, so as to fix the vertebrae and head, then these muscles, particularly the sternal portions, may assist in still further extending the neck, and carrying the head backwards, in consequence of their insertion being posterior to the centre of motion in the occipital condyles; this appears to be the case in tetanus : these muscles can also assist in laborious respi- ration, by raising and fixing the shoulders. This muscle is covered by the integuments, platysma, superficial fascia, external jugular vein, ascending branches of the cervical plexus of nerves, and by a small portion of the parotid gland ; it conceals part of the sternum and clavicle, of the sterno-hyoid, sterno thyroid, omo-hyoid, and digastric mus- DUBLIN DISSECTOR. 35 cles, also the lower part of the cervical vessels and several ganglia. The spinal accessory nerve perforates this mus- cle a little above its centre, and near its posterior surface ; this nerve is a division of the eighth pair, it distributes small branches to the mastoid and trapezius muscles, and joins freely with the cervical plexus ; the spinal accessory does not always perforate, but sometimes passes posterior to the mastoid muscle. [Varieties. The fissure between the sternal, and clavicular origins is sometimes wanting, the two origins being continuous ; sometimes there is an isolated fasiculus at its posterior margin ; sometimes its inferior extremity descends as low as to the rectus abdominis or even to the end of the sternum.] The student may remark that the two sterno-mastoid muscles bound a large triangular space situated on the fore- part of the neck, the apex at the sternum, the base at the jaw : this is divided by the mesial line into two lateral por- tions, which are named the anterior lateral triangles of the neck. Between the mastoid and the trapezius muscle also, on each side, a large triangular space is enclosed, the base form- ed by the clavicle, the apex by the mastoid process ; this space is called the posterior lateral triangle of the neck. Both these triangular regions may be observed to be sub- divided into two by the omo-hyoid muscle, which crosses the neck obliquely from the shoulder to the os-hyoides. Thus on each side of the middle line four triangle spaces may be noticed, principally formed by the trapezius, ster- no-mastoid, and omo-hyoid muscles ; these triangles are distinguished by the terms 1. posterior inferior ; 2. pos- terior superior ; 3. anterior inferior ; and 4. anterior supe- rior. The student should examine each of these regions, and consider the parts situated in them. These spaces can be ascertained during life, and therefore an accurate know- ledge of the contents of each may be of practical impor- tance. 1. The posterior inferior triangle is that small space behind the clavicular portion of the mastoid muscle, be- tween the clavicle and posterior belly of the omo-hyoid muscle ; in this space we find the subclavian artery, vein, and brachial plexus of nerves ; it is here that the operation of tying the subclavian artery, in case of axillary aneu- rism, is recommended to be performed. 2. The posterior su- perior triangle is above the posterior belly of the omo-hy- oid, and between the mastoid and trapezius muscles ; it contains the cervical plexus of nerves, several lymphatic ganglia, and a great quantity of cellular membrane. 3. The anterior inferior triangle is above the sternal third of the 36 DUBLIN DISSECTOR. clavicle between the median line and anterior belly of the omo-hyoid ; this space contains the carotid artery, jugular vein, and accompanying nerves, also the lateral lobe of the thyroid body, all of which are covered by the sterno-mas- toid, hyoid, and thyroid muscles. 4. The anterior superior triangle is between the sterno-mastoid and anterior belly of the omo-hyoid muscles ; the apex is formed by the decus- sation of these muscles, and is opposite the cricoid cartil- age ; the base is, superiorly, marked by the digastric mus- cle and lingual nerve ; this space also contains the great vessels and nerves, which here, however, are only super- ficially covered, so that in this situation the operation of tying the carotid artery can be more easily effected. Di- vide the sterno-mastoid muscle about its centre, and reflect each portion towards its attachment ; at the lower part of the neck, behind and between the sterno-mastoid muscles, are seen the following : STERNO-HYOIDEUS is long, flat, and thin, arises within the thorax from the posterior surface of the first bone of the sternum, cartilage of the first rib, sternal end of the clav- icle, and sterno-ciavicular capsule ; ascends obliquely in- wards, approximating its fellow above, and is inserted into the lower border of the body of the os hyoides, internal to the omo-hyoid, [with which it is here closely connected for a short distance.] Use, to depress the os hyoides, pharynx and larynx. This muscle is covered by the sternum and clavicle, by the sterno-mastoid and integuments ; it lies on the sterno thyroid, crico-thyroid, and thyreo-hyoid muscles, and on the thyroid body and its vessels ; a tendinous line often intersects it about its centre. [Varieties. This muscle sometimes is double, sometimes it arises from the middle of the clavicle, and at other times in common with the next muscle.] Cut this muscle across, and reflect each portion towards its attachments, and we see the following pair of muscles : STERNO-THYROIDEUS is broader and shorter than the last, arises from the posterior surface of the sternum and cartil- age of the second rib, ascends obliquely outwards, [diver- ging from its fellow,] and is inserted into the oblique line on the ala of the thyroid cartilage. Use, to depress the larynx. This muscle is covered by the sterno-mastoid and hyoid muscles, and by the skin ; it conceals the arteria and vena innominata, the carotid and subclavian vessels, and adjacent nerves, also the thyroid body, and the trachea ; between it and the latter there is a considerable quantity of cellular membrane, which contains several veins (infe- rior thyroid v.) Several filaments of the descendens noni nerve are distributed to this and to the former muscle. It DUBLIN DISSECTOR. 37 is between the sterno-thyroid muscles that the operation of tracheotomy is performed, while that of laryngotomy is between the sterno-hyoid muscles, and between the thyroid and cricoid cartilages* [Varieties. This muscle is sometimes double, sometimes lost upon adjoining muscles, and sometimes connected to its fellow by trans verse fibres.] OMO-HYOIDEUS is long, slender, and digastric, situated ob- liquely along the side and forepart of the neck, it arises broad and fleshy from the superior costa of the scapula behind its semilunar notch, from the ligament covering that notch, sometimes from the base of the coracoid pro- cess, and sometimes also from the acromial end of the cla- vicle ; it ascends obliquely forwards a little above the cla- vicle, passes beneath the sterno-mastoid muscle, where it is generally tendinous, except in the very young subject ; becoming again fleshy, it ascends nearly vertical along the outer side of the sterno-hyoid, and is inserted fleshy into the lower border of the os hyoides, at the junction of its body and cornu. Use, the muscle of one side cannot act independent of the other, both draw the os hyoides, phar- ynx, and larynx, downwards and backwards, and in deg- lutition serve to urge the food into the oesophagus. The origin of this muscle is concealed by the trapezius, it is anterior to the insertion of the levator anguli scapulae, and between the serratus magnus and supra-spinatus muscles ; the posterior belly is covered by the integuments and fas- cia, in some the clavicle overhangs it ; it divides the great posterior lateral triangle of the neck into an inferior and superior part, as was before mentioned ; this portion of the omo-hyoid can frequently be distinguished in the living neck. The tendon crosses the carotid artery and jugular vein, and is covered by the sterno-mastoid, which can thus move more easily on this structure. The anterior belly and insertion are covered by the integuments and fascia ; this portion of the muscle divides the anterior lateral tri- angle of the neck into an inferior and superior part. The omo-hyoid crosses over the scaleni muscles, the brachial plexus, phrenic, pneumogastric and sympathetic nerves, the carotid artery, jugular vein, and superior thyroid vessels. [Varieties. This muscle is sometimes double, and has one in- sertion into the side of the tongue. We have been informed of one subject, in which the muscle was entirely wanting on one side.] Beneath the three last described muscles, and lying on the trachea and sides of the larynx, is a large, soft, red mass, of a crescentic shape, the concavity directed up- wards ; this is the thyroid body ; it is in general larger and of a deeper colour in the child than in the adult or old 38 DUBLIN DISSECTOR, [subject] and in the female than in the male ; its size r how- ever, varies considerably in different individuals, even of the same sex and age. [Still its average weight may be set down as about one ounce in a state of health, in a diseased state it sometimes weighs as much as a pou?id and a half ; its transverse measurement is three inches and a quarter ; its vertical measurement a little over two inches.] It consists of two large pyramidal portions, called lateral lobes^ connected together by a narrow slip, the mid- dle lobv or isthmus ; the latter is thin and flat, and closely connected to the second, third, and fourth rings of the trachea ; the lateral lobes are plump and convex, large below, pointed above, placed by the side of the trachea and larynx, and extending as high as the ala3 of the thy- roid cartilage ; the left lateral lobe rests on the oesophagus, and both right and left overlap the carotid artery, inferior thyroid vessels, and recurrent nerve ; they are covered by the sterno-mastoid, hyoid, thyroid, and omo-hyoid muscles, by the platysma and skin ; they lie on the side of the trachea and larynx, on the crico-thyroid and inferior con- strictor of the pharynx. The middle lobe is very irregu- lar, it is sometimes deficient; in some cases it passes behind the oesophagus, or between this tube and the trachea a circumstance which might be productive of great incon- venience,, and even danger, in the event of enlargement of this body occurring in one in whom this malformation exist- ed. A narrow slip is often seen to ascend from the mid- dle lobe as high as the os hyoides, [being generally placed a little to the left of the median line ; following very nearly the course of this process, and frequently confounded with with it, is sometimes found a small muscle the levator glan- dula thyroidept u remarked, that if the tongue be protruded, the apex will he directed towards the affected side ; this phenomenon, which is only an apparent exception, depends in the action of the genio-hyo-glossus muscle of the healthy side, which will pull the base of the tongue on that side towards the chin, and must therefore turn the point to the opposite side. 5 50 DUBLIN DISSECTOR. stance of the tongue is composed of adeps blended with numerous muscular fibres derived from the stylo, hyo, ge- nio-hyo-glossi, and linguales muscles, and of many other fleshy fibres which do not properly belong to any of these [viz. the superficial transverse, and vertical lingual mus- cles :] two large arteries (lingual) and six considerable nerves (the gustatory, the lingual, and the glosso-pharyn- geal, on each side) supply this organ. The tongue is not only the organ of taste, but by its great mobility it assists in speech, in suction and in deglutition. The fifth pair of nerves endow the tongue with sensation and with the sense of taste, the ninth with mobility, and the eighth supply its base with sensation, and connect the motions of this organ with those of the pharynx and stomach. The tongue is subject to many morbid changes, viz. in- flammation, acute or chronic, causing great and dangerous, and sometimes fatal enlargement ; tumors of different kinds occur here, also ulceration, cancerous, syphilitic, apthous, &c. ; portions of this organ can be removed with safety, either by ligature or excision. [The tongue is sometimes the seat of congenital malformations ; its tip is sometimes bifurcated, sometimes nipple shaped ; the organ is sometimes entirely wanting, sometimes double. The fhenum lingucB (a vertical fold of the mucous membrane, as it is reflected from the inferior surface of the tongue to the floor of the mouth,) is sometimes too long, antero-posteriorly, or too short vertically, con. stituting the tongue tie, which interferes with nursing in the infant, and with distinct articulation at a subsequent period : this is easily relieved, by dividing the framum for a line or two. It has been sup. posed that in excising one lateral half of the tongue there would be serious hemorrhage, in consequence of a free anastomosis of the arte- ries of the two sides ; that this free anastomosis does not exist, is proved by minute injection, most of the vessels, terminating at the middle septum of the tongue ; it is also proved by the fact, that the lateral excision of the tongue, has been accomplished, without hemorrhage, by first tying the trunk of the lingual artery, just at the cornu of the os-hyoides.] SECTION IV. DISSECTION OF THE PHARYNX. To obtain a view of the muscles of the pharynx and pa- late, the student may now make the following dissection : divide the trachea and oesophagus in the lower part of the DUBLIN DISSECTOR. 51 neck ; detach them from the vertebrae, to which they are loosely connected; draw forward these organs, together with the vessels and nerves on either side ; place the saw flat on the bodies of the vertebrae ; insinuate its edge be- tween the styloid and mastoid processes on each side, and make a vertical section of the head : we have thus the face and anterior part of the cranium separated from the verte- bral column ; or, should it be desirable to preserve the cranium, we may separate the occipital bone from the at- las, and then remove from the subject the whole head, to- gether with the organs we wish to examine ; distend the pharynx with hair or tow, and remove some of the loose cellular tissue connected to it The pharynx is a large, muscular, and membranous bag. extending from the base of the cranium to the fourth or fifth cervical vertebra, where it ends in the oesophagus ; it is placed behind the nose, mouth, and larynx ; is some- what of an oval form, the largest part being opposite the os hyoides, and the smaller extremity joining the oesopha- gus. The pharynx is attached superiorly and posteriorly to the cuneiform process, by an aponeurosis, which is very strong in the middle line, laterally by a thinner aponeu- rosis to the petrous bone, and anteriorly, by fleshy fibres to the internal pterygoid plate and hamular process, and to the posterior part of the mylo-hyoid ridge of the lower maxilla ; the pharynx is connected posteriorly to the ver- tebra, and to the deep muscles of the neck, by loose reti- cular membrane; anteriorly it is attached by mucous membrane and muscular fibres to the cornua of the os hy- oides and thyroid cartilage, and to the sides of the cricoid, behind which the pharynx abruptly contracts and ends in the oesophagus : on either side of the pharynx, and loosely connected to it, is the sheath of the carotid artery with its .accompanying nerves. The muscular fibres which cover the back and sides of the pharynx, are named constrictor muscles ; they are symmetrical, and are three in number on each side, they are named the superior, middle, and in- j ferior ; they overlap each other, the inferior being most su- } perficial, the middle next, and the superior the deepest ; ! the constrictor muscles of opposite sides have one common I insertion into the middle tendinous line, or raphe on the back I part of the pharynx, which line is very strong and distinct i superiorly, being inserted into the cuneiform process, but interiorly it is weak and often indistinct. CONSTRICTOR PHARYNGIS INFERIOR is somewhat square, I arises from the side of the cricoid cartilage, from the infe- 'irior cornu and posterior part of the ala of the thyroid cartilage, external to the crico-thyroid andthyreo-hyoid ; 52 DUBLIN DISSECTOR. the superior fibres ascend obliquely, and overlap tke middle constrictor ; the inferior fibres run circularly and overlap the resophagus; inserted along with that of the opposite side into the middle line on the back of the pharynx ; its origin is covered by the sterno-thyroid mus- cle, and the thyroid body ; this muscle lies on the mucous membrane, except its superior fibres, which are separated from it by the middle constrictor. The inferior laryngeal or recurrent nerve passes beneath its lower edge, and the superior laryngeal beneath its upper. CONSTRICTOR PHARYNGIS MEDIUS is of a triangular form, arises from the cornu and appendix of the os hyoides, also from the stylo-hyoid and posterior thyreo-feyoid ligaments ; its fibres expand on the back of the pharynx, the superior ascend to the occipital bone, the middle run transversely, and the inferior descend beneath the lovrer constrictor, inserted into the mesial tendinous line or rapfee, and into the cuneiform process. The lingual artery and hyo-glos- sus muscle are connected to tb.e origin of this muscle, which part is separated from the inferior constrictor by the superior laryngeal nerve and cornu of the thyroid cartilage, and from the superior constrictor by the stylo- pharyngeus muscle and glosso-pharyngeal nerve ; on di- viding the edge of this muscle, the STYIJO-PHARYNGEUS ap- pears ; it arises from the root of the styloid process, des- cends to the side of the pharynx, where it expands between the superior and middle constrictors, and is inserted beneath the latter partly into the submucous tissue, and partly into the cornu of the thyroid cartilage, Cse, to elevate, dilate, shorten, and draw forwards the pharynx, in order to re- ceive the food from the tongue, it will also raise the larynx : divide the stylo-pharyngeus, and the superior constrictor will be exposed. CONSTRICTOR PHARTNGIS SUPERIOR, surrounds the superior part of the pharynx, arises by a dense aponeurosis from the petrous bone, which soon becomes connected with the next origin, which is fleshy, from the lower part of the internal pterygoid plate and hamular process, also from the intermaxillary ligament, (see page 7,) which connects it to the buccinator muscle, from the posterior third of the mylo-hyoid ridge, and from the side of the base of the tongue ; all the fibres take a semicircular course backwards and inwards, and are inserted into the cuneiform process and into the middle tendinous line on the back of the pharynx. The superior constrictor is covered by the sty- loid muscles and by the great vessels and nerves, and in- feriorly by the middle constrictor, from which the stylo- pharyngeus and glosso-pharyngeal nerve separate it : be- DUBLIN DISSECTOR. 53 tween the attachment to the petrous bone and that to the occipital, the mucous membrane is uncovered by muscular fibres in a small semicircular space, named sinus of Morgag- ni ; this is beneath the cuneiform process, on each side of the middle line, and corresponds to the Eustachian tubes ; between the temporal and pterygoid attachments, the mus- cles of the velum lie, and between the pterygoid and maxillary origins the internal pterygoid muscle and the gustatory nerve are situated. Use, the constrictors dimin- ish the capacity of the pharynx, and by the successive contractions of each, the food is forced into the oesophagus, the complex muscular structure of the pharynx may also assist in the modulation of the voice and in the production of certain sounds. Open the pharynx by a perpendicular incision through the middle tendinous line ; on looking into the cavity it will be found divided by the velum into iwo portions, a superior and inferior ; seven openings also may be remarked leading from it in different directions, viz. in the upper and nasal portion there are the two pos- terior nares, and on the side of each of these is the open- ing of the Eustachian tube ; below the velum is the isthmus faucium, or posterior opening of the mouth ; below and behind the tongue is the opening of the glottis ; and last- ly, the termination of the pharynx in the oesophagus. The openings of the nares are of an oval shape, their long diameter being vertical ; the body of the sphenoid bone bounds them superiorly, the palate bones inferiorly, the internal pterygoid plates externally, and the vomer sepa- rates them from each other : through these openings the air generally passes during respiration. The Eustachian tubes open on each side of the posterior nares, behind the infe- rior spongy bone; they are circular, and look forwards and inwards towards the septum narium, are formed of thick cartilage, covered by mucous membrane ; through these air is admitted from the nose into the tympanum, to support the membrana tympani on its inner side. The Eustachian tube must be again examined in the dissection of the organ of hearing.* Beneath the velum is the isth- mus faucium, transversely oval, but capable of great change in figure and size, bounded above by the velum and uvula, below by the tongue, and on either side by the pillars or arches of the palate, and by the amygdalae. The opening of the glottis or superior opening of the larynx, is at the lower and anterior part of the pharynx, behind the * The student may practice the introduction of a probe into this tube : slightly curve a blunt probe, pass it along the floor of the nose to the posterior nares, .then direct its extremity upwards, outwards, and backwards, that is, towards the ear, and it will enter this tube. 5* 54 DUBLIN DISSECTOR. epiglottis, and rather beneath tfee tongue ; it is of a trian- gular form, the base anteriorly, formed by the epiglottis ; the sides are composed of fcJ.ds of mucous membrane, termed aryteno-epiglottidean, and the apex, which is pos- teriorly, is formed by the appendices of the arytenoid cartilages. The glottis, which will again be considered in speaking of the larynx, is always open, except in the act of deglutition. The asopliage&l opening is below and be- hind the glottis ; it is always closed, except in deglutition. The student should next examine the velum pendulum pa- lati, o? palatum molle. SECTION V. DISSECTION OF THE PALATE AND ITS MUSCLES. THE velum pendvJum palati is a soft moveable substance, attached superiorly and anteriorly to the hard palate on each side of the tongue and pharynx, and posteriorly and inferiorly it terminates in 8. thin edge, from the centre of which the uvwia descends, thus giving a lunated appear- ance to tfee edge of the velum on each side ; these crescen- tic edges are named the half arches of the palate, [Being two in number on each side, between which the tonsils are placed 5 the space bounded anteriorly and posteriorly, by these half arches, or pillars, is the fauces, *md the anterior opening into this space is called the isthmiie .faucium.'-. The velum is situated obliquely, its fixed edge being su- perior and anterior to the loose, one surface looking for- wards asd downwards towards the moulh and tongue, the opposite surface looking upwards and backwards ; during life this aspect can be altered by the auction of muscles, which can cither elevate, depress, or make tense the velum. Beneath the mucous membrane of the velum several small glands are situated, chiefly on the inferior surface. The -a vula is a conical prolongation of the velum, enclosing small glands, loose cellular membrane, and some muscular fibres ; in deglutition, the velum and uvula are raised so as to touch the back part of the pharynx, and thus they are of use in preventing the food ascendmg into the cppcr or nasal part of the cavity, from which it might regurgitate into the nates* The muscles of the velum or soft palate be levator and tensor palati, the moto uvula?, palato-glossus and palato-pharyngeus. DUBLIN DISSECTOR. 55 LEVATOR-PALATI, arises narrow from the petrous bone, in front of the foramen caroticum and behind the Eustachian tube, descends obliquely inwards and backwards, and is inserted broad into the velum near its centre ; its name de- notes its use. It is situated on the side of the posterior nares, its insertion intermixes with its fellow and with the other muscles of the palate. TENSOR-PALATI vel circumflexus palati, arises fleshy from a depression at the root of the internal pterygoid plate, from the spinous process of the sphenoid, and from the forepart of the Eustachian tube, descends between the in- ternal pterygoid plate and muscle, ends in a flat tendon, which turns round the hamular process inwards to the vel- um, it then expands, and joins that from the opposite side. Use, to make tense, the velum in a horizontal direction be- tween the hamular processes. MOTOR UVULAE, arises from the posterior extremity or spine of the palate bones, descends close to its fellow, along the median line of the velum, and is inserted into the cellular tissue of the uvula. Use, to raise and shorten the uvula : this pair of muscles are so close that they appear but as one, hence they have sometimes received the name of azygos uvula* PALATO-GLOSSXJS vel constrictor isthrai faucium, or thr anterior arch or pillar of the palate, arises from the inferi- or surface of the velum, descends forwards and outwards, enclosed in a fold of mucous membrane anterior to the tonsil. Inserted 'into the side of the tongue. Use, to elevate the tongue or to depress the velum ; this pair of muscles may also close the fauces. PALATO-PHARYNGEUS, or posterior arch of the palate, a ri- ces broad from the inferior surface of -the palate, arcfces downwards and backwards behind the tonsil, and is inser- ted into the side and back of the pharynx, and into the -cornu of the thyroid cartilage, its fibres mixing with those of the stylo-pharyngeus. Cse, to elevate the pharynx, like Uie stylo-pharyngei in the commencement of deglutition-; but afterwards to depress the velum. The tonsil or amygdala, though apparently a compact ftody, is formed of a congeries of mucous glands, of an ir- Tegular figure, somewhat oval, the larger extremity abova, placed ina triangular recess between the pillars of the palate, above the side of the base of the tongue, covered internally by the mucous membrane, and externally by the 'superior constrictor of the pharynx ; small holes are re- marked on its surface ; these lead into cells from which the mucus can be expressed. [The tonsil is usually described, as being of the size of an almond : 56 DUBLIN DISSECTOR. it is from six to eight lines in length, from four to five in breadth, and three in thickness, and is of a reddish grey color.] The amygdalae are very vascular and secrete a viscid fluid, which being pressed out in the moment of deglutition by the contraction of the surrounding muscles, serves to lubricate the alimentary bolus in its passage. The inter- nal carotid artery is posterior and somewhat external to it, the external carotid is also to its outer side, and the facial artery, just before it enters the submaxillary gland, is an- terior to it ; from these three vessels, this gland when of its healthy size, is separated by the superior constrictor, and by a considerable interval which is rilled by cellular tissue, but when enlarged, as in the case of abscess, it comes into such close contact with these, particularly with the inter- nal carotid, that there is some danger of wounding the lat- ter in opening the abscess with the lancet. The soft palate and its arches, the uvula and the tonsils, are liable to many morbid affections, viz. acute inflamma- tion and all its consequences ; syphilitic ulceration very commonly attacks these parts, particularly that surface, towards the mouth ; polypi, also, are not unfrequently pro- duced from the velum, and in general from its upper or nasal surface. When the uvula is the seat of inflamma- tion, its pendulous extremity becomes so distended by se- rous infiltration, that its figure is totally changed, and it sometimes interferes so much with deglutition and respi- ration, or excites such irritation, as to require free scarifi- cation, or excision of its lower portion. The velum is sometimes found cleft at birth with or without the accom- panying similar anormal state of the hard palate and up- per lip. The tonsil is very subject to acute inflammation (cynan- che tonsillaris) ; in this affection it enlarges so much as to impede deglutition, induce deafness, and even in some -cases to threaten suffocation. It is sometimes, also, the seat of chronic enlargement, to such a degree, as to require the operation of removal ; it is also frequently affected with syphilitic, ulceration. [The tonsil is sometimes the seat of a calcareous concretion ; the chronic cases of hard enlarged tonsils, are commonly spoken of as schirrus ; it is not however of a cancerous nature. True cancer here is exceedingly rare. Gross has been unable to find a single case re. corded, but one instance of the kind has come to our knowledge, and of that case the minutes are in the possession of Prof. Parker.] The (Esophagus appears as the continuation of the phar- ynx, it differs from it, however, in structure ; the mucous membrane is paler, and thrown into longitudinal folds ; the muscular fibres are arranged in two laminse, the external DU-BLIX DISSECTOR. 57 s,Te longitudinal, strong and red, attached superiorly and anteriorly to the criccM cartilage, and below are lost on the stomach; the internal circular fibres are pale, and cease abrubtly at the cardiac oriice of the stomach. [According to some anatomists, the circular fibres of the' oesophagus do not terminate at this point, but are collected into two bands, on of which is situated at the left of the orifice of the stomach, and is thence distributed over its anterior and posterior faces, while the other f s at the right of the orifice and is thence distributed over the ante- dor and posterior faces of the greater cul de sac, if so they must de- cussate each other, and form a sort of sphincter muscle, around the orifice.] In the neck the (Esophagus descends posterior to the tra- chea, and nearly in the ^middle line ; it inclines a little to the left side below, so as to be uncovered by that tube ; the left lobe of the thyroid gland, the recin rent nerve, and the in- ferior thyroid "vessels, He on it in this situation. The morbi?' appearances met vrith in the pharynx and 'oesophagus are not very many ; tke mucous membrane of the former is liable to inflammation, (cynanche pkaryngea,) and to ulceration from various causes ; the subnaucous tis- sue is frequently the source of polypous growths, particu- larly at the upper part. The lining membrane of the oesophagus is seldom the seat of active inflammation, ex- cept as the consequence of some foreign body, or the con- tact of some acrid substance ; it is not unfrequently the seat of stricture, caused in some cases by a contraction and thickening of its coats, in others by true scirrhus, ending in cancerous uiceration ; tumours in the vicinity of this tube will also interrupt its functions, for example, bronchocele, charged bronchial ganglia, cr aneurism 'of the descending aorta. The cesophogus is also sometime? affected with paralysis, and in hysterical patients it is very subject to nervous affections, which frequently bear a close resemblance to true stricture of this tube. The course and connexions of the oesophagus in the chest will be seen hereafter. 1 '" [This organ is the seat of various congenital malformations ; it may be double or entirely wanting, the pharynx ending in a blind cul-de-sac : it may terminate in a blind cul-de-sac just below the pharynx or near the cesophageal extremity of the stomach : it may end in the trachea, and it may be preternaturally dilated or contracted. Stricture usually occurs a short distance below the pharynx, and if treated early with bougies may be cured, it is sometimes spasmodic.] * The student should practice the passing of a probe or canula armed with a ligature, along the nares into the pharynx, and endeavour to enclose the uvula in the noose, thus imitating the operation of tying polypi when situated in the phary- nx, on the velum, or in the posterior nares ; lit: may also puss a flexible tube into 58 DUBLIN DISSECTOR. SECTION VI. DISSECTION OF THE LARYNX. The larynx is composed of several cartilages and muscles; it is placed at the anterior part of the neck, between the tongue and trachea, and in front of the pha- rynx and oesophagus, it is suspended by the muscle and ligaments from the os hyoides-, this bone is connected to the chin by several muscles, and to the styloid process of the temporal bone on each side by the digastric and stylo- hyoid muscle and ligament ; it consists of five parts, the middle portion, or body, is very rough and convex anterior- ly and superiorly for the attachment of muscles, concave posteriorly and inferiorly where it covers the epiglottide- an gland ; from the body the cornua pass off, one to either side, giving attachment to muscles above and below, lined by mucous membrane, and serving to expand the pharynx and fauces ; where each cornu joins the body, a small process, the appendix, ascends obliquely backwards, and gives attachment to the stylo-hyoid ligament and muscle. Use, to serve as a fixed point for the muscles of the tongue, pharynx and larynx. Four cartilages enter into the formation of the skeleton of the larynx, the thyroid, cricoid and two arytenoid, and one fibre-cartilage, the epiglottis. The thyroid cartilage is placed at the anterior and lateral parts of the larynx ; it presents, anteriorly, a prominence, named, in the male subject, the pomum Adami, laterally the alec, each of which, in passing backwards, increases in depth, and presents an oblique ridge for the attachment of the sterno-thyroid, and thyreo-hyoid muscles ; a hole is frequently observed in each ala near this ridge ; posteriorly the alee terminate round and thick, and from their upper and lower extremities send the pharynx, and thence direct it to the stomach or into the larynx ; any practi- tioner may be suddenly called on to use the stomach pump, in case of poison having been swallowed, or to inflate the lungs in asphyxia : in theirs* case, when the tube has passed into the pharynx, from the mouth or nares, the tongue should be pressed back, so as to close the glottis, and the end of the instrument should te kept close to the vertebrae to avoid irritating or pressing on the epiglottis: in the second cose, the tube should be passed through either naris into the pharynx, the forceps or the finger of the surgeon, introduced into the mouth, can then guide it downwards and forwards to the glottis ; at this time, however, the tongue should 'be drawn forwards ; thus the epiglottis will be raised and the glottis opened oppo- site the edge of the velum ; the tube may then be urged into the larynx, and arti- ficial respiration commenced. In conducting this process it is advisable to press the upper part of the trachea gently against the vertebra;, so as to fix the larynx and the tube, as well as to guard against the admission of air into the oesophagus, and the consequent inflation of the stomach. DUBLIN DISSECTOR. 59 off the processes called cnrnua ; the ascending cornua are connected to those of the 's hyoides by round ligaments, [the lateral hyo-thyroid] which are often cartilaginous, and sometimes even bony ; the inferior cornua are shorter, and are attached by the lateral crico-thyroid ligaments to the sides of the cricoid cartilage ; the anterior angle of the thyroid is connected superiorly to the body of the os hyoi- des by a thin membrane, anterior hyo-thyroid ligament, and interiorly to the cricoid cartilage by a strong elastic liga- ment, crico-thyroid. The cricoid, or annular cartilage, forms the lower part of the larynx, is narrow before, deep behind ; the inferior edge or circumference is nearly horizontal ; the superior is oblique, leading from above and from be- hind, downwards and forwards- ; on its posterior surface is a middle prominent ridge, on each side of which is a de- pression, filled by the posterior crico-arytenoid muscle ; at the upper and back part on each side is a smooth articu- lating convex surface, on which each arytenoid cartilage moves. [This is a diarthrodial articulation, having a small synovial mem- brane.] The arytenoid cartilages are triangular, the base below moving on the cricoid, the apex above inclining a little backwards, and surmounted by a small process, the appen- dix ; the internal, or opposed side of each cartilage is flat, the external is rough for the insertion of muscles, the pos- terior surface of each is concave, and covered by the ary- tenoid muscle ; the anterior is sharp, and connected supe- riorly to the epiglottis by the aryteno-epiglottidean folds of mucous membrane, which folds form the sides of the glottis, and inferiorly to the angle of the thyroid by two ligaments on each side, called, thy reo-aryteno id, or chorda xo- cales : these arise from a sharp projection on the forepart of the base of each arytenoid, pass forward converging, and are inserted into the angle of the thyroid ; the inferior is the stronger, it is tendinous and horizontal, the superior is membranous and semilunar ; the narrow passage be- tween these ligaments of opposite sides is called the rima glottidis ; between the superior and inferior ligament of each side is a scmilunar fossa called the sinus or ventricle of the larynx. The epiglottis, or fibro-cartilage, is anterior to the glottis ; it is somewhat of an oval form, connected inferiorly at its origin by a stalk-like process to the notch or angle of the thyroid cartilage ; anteriorly by cellular membrane and by the epiglottidean gland to the os hyoides, also to the tongue by three folds of mucous membrane, the central 60 DUBLIN DISSECTOR. one of which is called the fr&num epiglottis ; posterior- ly to the arytenoid cartilages by the folds of mucous mem- brane, which form the sides of the glottis. The epiglottis stands nearly vertical ; it is a little curved forwards at its upper border and along its sides, so that its anterior sur- face is concave from above downwards, and convex trans- versely ; and its posterior surface is concave from side to- side, and convex from above downwards ; it is very elas- tic, and never found ossified, a change which the cartilages of the larynx are prone to undergo. In deglutition the epi- glottis is of much use ; it covers the larynx, and so prevents- any foreign substance entering it : during this act the tongue is turned backwards,, and the larynx raised for- wards ; thus the glottis is closed, and the contents of the mouth pass over the epiglottis into the pharynx. The la- rynx is lined by mucous membrane, which passing from the tongue and pharynx, covers the epiglottis and aryte- noid cartilages, forms their connecting folds, descends into the larynx, covers the chordae vacates., lines the ventricles of the larynx>, and is continued down through the trachea and the branches of that tube ; it is bu* loosely connected to the cartilages above at the gk>ttis 7 b^t more closely be- low ; several mucous glands are connected to it* thus in. the arytene-epiglofc&dean fold of each sMe there are small glands cal]jed arytenoid,, and in front o:!? the epiglottis, be- hind the 3 hyokles., tfee epiglottifasm glamd is situated ; this opens by sraall' ducts on the posterior or laryngeal surface of the epiglottis, The openings of the larynx are two, th(y superior or ihc glottis? and tke iwj&riw or the rima glottldis.. The opening of t]?_/s glottis has been already noticed ; it is-, immediately behkiii the tongiie aad epiglottis, and is of i\ triangular form., the base anteriorly. (See page 53.) The* rima glottidis- is thane quarters of an inch below the glottic; it is like a slit, be^ig very narrow frosa side to side, and oif a triangular figure, the base posteriorly formed by the- bases of the arytenoid, and by the upper and posterior edge of the cricoid ; the apex is anteriorly in the angle of the thyroid cartilage, tiie chorda) vocales form the sides : be- low the rima glottiiis the larynx enlarges within the cri- coid cartilage, and is of a circular figure, and soon termi- nates in the trachea. The muscles of the larynx are sym- metrical, they are found on the front, sides and back part ; those on the forepart are the thyreo-hyoid, and the crico- thyrpid ; on each side are the thyreo and lateral crico-ary- tenoid, and posteriorly are the arytenoid and posterior cri- co-arytenoid. THYREO-HYOIDEUS-> broad and flat, arises from the upper edge of the oblique ridge on the ala of the thyroid carti-. DUBLIN DISSECTOR. 61 lage, ascends a little outwards, and is inserted into the lower border of the cornu of the os hyoides. Use, to elevate and draw forwards the larynx beneath the tongue and epiglot- tis, and so cause the glottis to be closed in deglutition. This muscle is partly covered by the integuments and ster- no and omo-hyoid ; it appears like a continuation of the sterno-thyroid. CRICO-THYROIDEUS, inferior to the former, short and trian- gular ; arises narrow from the forepart of the cricoid carti- lage, ascends obliquely outwards, and is inserted broad into the lower border of the thyroid. Use, to approximate these cartilages, and to depress and draw forward the thyroid, also to raise and draw backwards the cricoid cartilage, and thus make tense the chordae vocales. The crico-thyroid ligament occupies the space between these muscles ; they are covered by the sterno-hyoid. Raise the ala of the thy- roid cartilage on one side, and the lateral muscles of the larynx will be exposed. THYREO-ARYTENOIDEUS is flat and thin, arises from the pos- terior surface of the thyroid cartilage near its angle : the fibres pass backwards and outwards, expanding over the side of the rima glottidis, and are inserted into the anterior edge of the arytenoid cartilage. Use, to draw the cartilage forward and towards its fellow, thereby diminishing the capacity of the rima glottidis ; these muscles can also pro- duce various alterations in the form, position, and degree of tension of the chordas vocales, which they cover, and they can compress the sinus or sacculus laryngis. The thyreo-arytenoid muscles are considered by some as the principal and most important agents in the production of voice, in consequence of their proximity to the vocal chords, and their capability of producing endless varieties in their condition, causing the vibration in their edges so to differ in intensity and duration, as to produce, from the air passing over them, (to a certain extent only,) corres- ponding varieties of sound or tone. These muscles are covered by the aloe of the thyroid car- tilage ; they lie on the chordce vocales, and on the inter- mediate sinus ; superiorly, their fibres extend to an indefi- nite height in the mucous folds of the glottis, and inferiorly they are connected to the following muscles, CRICO-ARYTENOIDEUS LATERALIS, arises from the upper edge of the side of the cricoid cartilage, where the latter is covered by the ala of the thyroid cartilage ; ascends ob- liquely backwards, inserted into the base of the arytenoid. Use, to draw that cartilage forwards and outwards, and thus to relax the vocal chords, and enlarge the rima from side to side, but contract it from before backwards. Raise 6 62 DUBLIN DISSECTOR. the mucous membrane on the back part of the larynx, to expose the muscles situated there. CRICO-ARYTENOJDEUS POSTICUS, strong and flat, arises from the depression on the posterior surface of the cricoid ; the fibres ascend obliquely outwards, inserted by a tendon into the outside of the base of the arytenoid cartilage. Use, to draw this cartilage backwards and outwards, so as to en- large the rima in every direction, as in full inspiration. These muscles lie on the back of the cricoid cartilage, and are covered posteriorly by the pale mucous membrane de- scending into the oesophagus : these and the crico-thyroid muscles are the dilators of the rima glottidis. ARYTENOIDEUS, fills the interval between the arytenoid cartilages, and is enclosed in a fold of mucuous membrane : it consists of oblique and transverse fibres ; the former con- sist of two or three fasciculi, which pass from the apex of one cartilage to the base of the opposite ; the transverse fibres are more numerous, and are attached to the posteri- or surface of each cartilage. Use, to approximate these cartilages, and close the sides of the rima : these, together with the thyreoand crico-ary tenoidei laterales are the con- tractors of the rima glottis. In the aryteno-epiglottidean folds, fleshy fibres are sometimes discernible, and have been described as distinct muscles, and named from their situation, aryteno-epiglottidean and thyreo-epiglottidean or the depressors of the epiglottis. In the human subject, how- ever, these are never sufficiently well marked to merit the apellation of distinct muscles. The arteries which supply the larynx are derived from the superior and inferior thyroid ; the former is a branch of the external carotid, the latter of the subclavian. The laryngeal nerves are four in number, two on each side, the superior and inferior ; both are derived from the par vagum or pneumo-gastric ; the former arising from it near the base of the cranium, the latter, on the right side, comes off from this trunk at the lower part of the neck, and on the left side it arises from it in the thorax, below the arch of the aorta: the inferior laryngeal nerves are principally distributed to the muscles, and the superior to the mem- brane and glands of the larynx, but not exclusively so. The inferior supplies the posterior and lateral crico-ary- tenoid andthe thyrco-arytenoid muscles ; the superior sends a large branch to the arytenoid, and a small, but very long filament to the crico-thyroid muscle ; several branches of this nerve are distributed to the epiglottis and to the mucous membrane at the glottis, which in this situation possesses great sensibility. From this view it would appear that the inferior laryngeal nerve supplies the dilating muscles of DUBLIN DISSECTOR. 63 the larynx which are the principle agents in voice, while the superior supplies those which close the glottis, as also the lining membrane, which possesses very peculiar and very delicate sensibility. [For the anatomy of the trachea, see p. 93.] The larynx and trachea are subject to many morbid changes of which the mucuous membrane is most com- monly the seat ; inflammation of that lining the larynx is named cynanche laryngea, or laryngitis, of that lining the trachea, cynanche trachealis, or croup ; in the latter case an exudation of lymph, or a false membrane is usually formed in the trachea., in the former case, effusion of serum in the loose submucous tissue, or oedema of the glottis, is a frequent and often fatal effect ; ulceration, the effect of inflammation, is not uncommon about the glottis: syphilis and phthisis also occasionally induce ulceration in this part, and even involve the epiglottis and the arytenoid car- tilages. [In ulceration of the cartilages, large pieces are sometimes thrown off, but these organs are more prone to ossification, particularly in ad- vanced life : the thyriod and cricoid cartilages, are most commonly affected and it is said that no cases of ossification of the arytenoids. or epiglottis have been recorded. There is however in the college museum a specimen of very complete ossification, of the thyroid cricoid, and both arytenoid cartilages. Polypes are sometimes found within the larynx. The muscles of the larynx are also sometimes diseased, either being infiltrated with tuberculous matter, or else being in a state of atrophy, hence causing alterations in the voice : foreign bodies may from their size be arrested in the calibre of the larynx, or if small they may be lodged in its sinuses ; the term bronchotomy as applied to operations upon the larynx or trachea, is manifestly im- proper, there being in fact no such operation as bronchotomy, which implies a section of the bronchial tubes, and they are beyond the reach of the surgeon.] Foreign bodies impacted in the lower part of the phar- ynx, or when engaged in the larynx, or when fallen into the trachea, may cause such suspension of respiration as to call for the operation of bronchotomy ; suspended ani- mation, also, from any cause, or any tumour in the fauces which impedes respiration, may require the same means ; this operation is two-fold, laryngotomy and tracheotomy ; in the first the air tube is to be opened through the crico- thyroid ligament, in the second through the fourth, fifth, and sixth rings of the trachea. 64 DUBLIN DISSECTOR, SECTION VII. DISSECTION OF THE DEEP MUSCLES OF THE NECK. THESE muscles, which are seven in number on each side, form the third layer of the cervical muscles ; they lie close to the vertebrae, and are exposed by removing the pharynx, larynx, cervical vessels and nerves. LONGUS COLLI extends from the third dorsal vertebra to the atlas ; it arises from the sides of the bodies of the three superior dorsal and four inferior cervical vertebrae, from the inter vertebral ligaments, also from the head of the first rib, and from the anterior tubercles of the transverse pro- cesses of the four last cervical vertebrae ; the fibres ascend obliquely inwards, adhering to each bone in their course, and are inserted into the forepart of the first, second, and third cervical vertebrae. Use, to bend the neck to one side, and rotate the atlas on the dentata ; or, if both muscles act, to bend the neck directly forwards. This muscle ap- pears to consist of an inferior and superior portion ; the first arising from the bodies of the dorsal is inserted into those of the inferior cervical vertebrae ; the second arising from the transverse processes of the third, fourth, and fifth cervical vertebra?, is inserted into the bodies of the first and second. These muscles, like most of those which ad- here to the vertebrae, though long, yet consist of short fibres which pass from one bone to another, are generally intermixed with tendinous substance, and are irregular as to the number of the vertebrae to which they are attached. RECTUS CAPITIS ANTICUS MAJOR, long and flat, arises by small tendons from the anterior tubercles of the transverse processes of the four last cervical vertebrae ; they soon unite in a fleshy substance which ascends obliquely in- wards, and is inserted broad into the cuneiform process of the occipital bone. Use, to bend forwards the neck and head. This muscle lies behind the carotid artery and sym- pathetic nerve, and between the longus colli and scaleni. Separate this muscle from its insertion, and we expose the following : RECTUS CAPITIS ANTICUS MINOR, short and narrow, arises from the transverse process of the atlas, ascends inwards, and is inserted into the cuneiform process. Use, to bend the head forwards and to one side on the atlas : this muscle lies to the outer side, but is in part concealed by the last. RECTUS CAPITIS LATERALIS, very short, arises from the transverse process of the atlas, ascends, and is inserted into DUBLIN DISSECTOR. 65 the semilunar ridge or jugular process of the occipital bone, which extends from the condyle to the mastoid pro- cess. Use, with the last muscle it can bend the head for- wards or incline it to one side. This muscle is external to that last described ; it lies on the vertebral artery, and is covered by the jugular vein. SCALEJSUS ANTICUS, arises tendinous from the anterior tubercles of the transverse processes of the third, fourth, fifth, and sixth cervical vertebrae ; the fibres descend ob- liquely forwards and outwards, form a flat muscle, which is inserted tendinous into the upper surface of the first rib, near its cartilage. Use, to bend the neck forwards and laterally, also to elevate and fix the rib as in inspiration. The phrenic nerve descends on the anterior surface of this muscle ; the subclavian vein crosses its insertion ; the omo-hyoid and sterno-mastoid lie anterior to it ; the sub- clavian artery and brachial plexus are behind it, and the vertebral vessels separates it from the longus colli. SCALENUS MEDIUS, arises from the posterior tubercles of the transverse processes of four or five inferior cervical vertebrae, by small tendinous fibres ; these become fleshy, and descend obliquely outwards and backwards, and are inserted into the upper surface of the second rib behind the subclavian artery. Use, similar to the last. This muscle is covered by the brachial plexus, subclavian artery, and anterior scalenus. SCALENUS POSTICUS, arises from the posterior tubercles of two or three lower cervical vertebrae, descends behind the former, and is inserted into the upper edge of the second rib, between its tubercle and angle. Use, to elevate the second rib, to bend the neck to one side, and a little back- wards. One or two branches of the brachial plexus some- times separate this from the middle scalenus, at other times there is no distinction between them, excepting in their in- sertion : behind the posterior scalenus lie the transversalis and splemus colli, also the levator anguli scapulas, which muscles cannot be examined at present [Varieties. The fasciculi of the scaleni muscles, are variable, and are more or less run together, so that the number described varies with different anatomists, from Chaussier, who describes but one, to Albinus who makes five.] We shall next proceed to the dissection of the thorax. 6* 66 DUBLIN DISSECTO> CHAPTER III. DISSECTION OF THE THORAX. SECTION I. OF THE MUSCLES ON THE ANTERIOR AND LATERAL PARTS OF THE THORAX. MAKE one incision through the integuments along the clavicle, a second from the upper end of the sternum tc the ensiform cartilage, and from this point carry a third towards the shoulder ; reflect the integuments and subja- cent cellular membrane from within and from below, up- wards and outwards, and thus the great pectoral muscle will be exposed, the dissection of which will be facilitated if its fibres be made tense by separating the arm from the side.* Beneath the integuments in the female we find the mammary gland ; this is a conglomerate gland, imbedded in fat, hemispherical, flat posteriorly, convex anteriorly, sur- rounded by a capsule of condensed cellular membrane, which is loosely connected to the pectoral muscle, and sends processes into the gland to support and connect its several lobules ; these last are very soft and pale, almost white ; from each of them small ducts arise, which uniting together form larger tubes ; these converge towards the root of the nipple, where they expand into sinuses, from which smaller ducts proceed and open on its surface : the skin covering the breast is soft and delicate, and about the centre of it, is the conical projection called the nipple, near the point of which the lactiferous ducts open ; the base is surrounded by an areola of a dark colour. This gland will be found to differ in structure in different subjects ; in some the capsule is indistinct, and the lobules scattered, or more separate than usual ; in some it has a redder appear- ance than in others, and it frequently feels unusually hard or rugged, although free from disease. [This gland is of a light pink color ; it is difficult to lay down any rule, as to its volume, for it is very small, up to the age of puberty, when it rapidly increases in development, and it reaches its maximum *The student of some experience, instead of removing the skin from this region, according to the above directions, may rather practise the operation of extirpation of the breast, which can be easily accomplished by two seimelliptical incisions, one below, and the other above the gland, through the integuments and nearly parallel to the fibres of the great pectoral muscle, from which the gland can be then easily detached, unless disease should have caused any very close adhesion. DUBLIN DISSECTOR. 67 during gestation and lactation, and again after the period of child bearing is past, it becomes atrophied, and even confounded with the surrounding cellular tissue ; if separated entirely from the adjoining cellular and adipose tissue and placed upon a flat surface, it is found to be of a circular form having a diameter of from three to five inches, and a thickness of from ten to fifteen lines. It is said that the left mamma is usually somewhat larger than the right. These organs in connexion with their functions constitute the characteristic of one of the zoological classes of animals, the mammalia. The organs exist in the male subject though not usually developed, except in some rare instances in which they have afforded an abun- dant secretion of milk. On the surface of the areola, there are a number of small tubercles surrounding the nipple, which are particularly prominent in pregnant, and nursing females, it has been supposed that these bodies secreted an oleaginous substance, to protect the nipple, and guard it against excoriation, while nursing, but there are several circumstances which go to prove that they are of the same structure as the mamma, itself, and that they secrete milk. The mammas arevery abundantly supplied with blood, by the external thoracic, intercostal, and internal mam- mary arteries also with nerves from the intercostals and axillary plexus.] The female breast is the seat of many morbid changes, viz. inflammation, and suppuration, either in the body of the gland, or in the cellular tissue around it or behind it, that is between it and the muscle enlargement atrophy tumours of various kinds, adipose, hydatid, cartilaginous, scirrhus, cancerous, &c. ; some indolent, chronic, andinnoc- cuous, others more rapid in their progress, fungoid, and malignant. [Hypertrophy of the breast, sometimes occurs in the male, and in the female it occasionally acquires an enormous magnitude ; cases being recorded, in which it weighed fifteen, twenty, and even sixty four pounds. Encephaloid disease and calcareous formations, and neuralgia also occur ; apoplexy of the breast is an affection peculiar to young girls, coming on just before the establishment of the men- strual secretion and disappearing soon after. Carcinoma sometimes occurs in the male breast ; in male infants a few days old, the breasts sometimes become swelled, red, and painful, and by gentle pressure a fluid resembling milk is forced out. Additional nipples are not un- common, and occasionally a supernumerary mamma exists, a case is recorded in which the additional organ occupied the left groin, and secreted milk freely.] PECTORALIS MAJOR, flat and triangular, arises somewhat tendinous from the sternal half of the clavicle, from the anterior surface of the sternum, fleshy from the cartilages of the third, fourth, fifth, and sixth true ribs, and from an aponeurosis common to it and the external oblique muscle ; the clavicular fibres descend, the sternal pass horizontally, and the costal ascend obliquely ; all pass outwards in front 68 DUBLIN DISSECTOR. of the axilla towards the humerus, into which they are inserted by a flat tendon into the anterior edge of the bici- pital groove, and by an aponeurosis into the fascia of the arm ; a line of cellular membrane separates the clavicular from the sternal portion ; in some cases these appear as distinct muscles. Use, the clavicular portion can raise the arm and draw it forward, the sternal can press it to the side, particularly if assisted by the latissimus dorsi, and the costal portion can draw it downwards and forwards : the whole muscle will draw the arm forwards and inwards on the chest : if the arm have been rotated outwards, it can roll it inwards, and so pronate the hand ; if the arms be fixed, and this pair of muscles act, they will draw the ribs upwards and outwards, and thus by enlarging the thorax assist in inspiration. This muscle is covered by the skin, platysma and mammary gland, and its insertion is partly concealed by the deltoid ; it covers a portion of the ster- num and of the true ribs, also the subclavian and lesser pectoral muscles, the coraco-clavicular ligament, the tho- racic and axillary vessels and nerves. Between the clavi- cular portion of "this muscle, and the anterior edge of the deltoid, is a space filled by cellular tissue, the cephalic vein and a small artery, [a branch of the thoracica acro- mial.] The tendinous fibres of the sternal portions of op- posite sides decussate each other, and cover the sternum with a sort of aponeurosis ; the insertion has a twisted appearance in front of the axilla, the sternal and costal portions being folded behind the clavicular, and inserted superior and posterior to it into the anterior edge of the bicipital groove, while the clavicular is united to the del- toid, and is inserted into the humerus along with that mus- cle ; in some subjects a bursa may be found between these two insertions of the pectoral muscle. From the lower edge of the costal portion a fleshy slip sometimes descends and joins either the rectus or external oblique muscle of the abdomen ; and in some a strong muscular band con- nects it to the inferior margin of the latissimus dorsi. [Other varieties. Sometimes this muscle is attached by a fasci- culus to the brachialis internus, sometimes a fasciculus comes off towards the axilla, is converted into a tendon, and finally inserted into the internal tuberosity of the os humeri ; sometimes a fasciculus comes off from its tendon, crosses its insertion, and the bicipital groove of the os brachii, and is blended with the tendon of the supra spinatus.] Make a perpendicular division of this muscle, reflect the edges, one towards the sternum, the other towards the shoulder ; and the lesser pectoral and subclavian muscles come into view. PECTOEALIS MINOR, flat and triangular, arises from the DUBLIN DISSECTOR. 69 external surface and upper edge of the third, fourth, and fifth ribs, sometimes from the second, external to their car- tilages ; the fibres ascend, obliquely outwards and back- wards, and converging, end in a flat tendon, which is in- serted into the inner and upper surface of the coracoid process, near its anterior extremity, being here connected with the coraco-brachialis and short-head of the biceps ; a band of this tendon frequently passes over this process through the triangular ligament, and is connected to it, or to the tendon of the supra-spinatus, or to the capsular li- gament of the shoulder. Use, to draw the shoulder for- wards, downwards, and inwards, also to assist the great pectoral in elevating the ribs in inspiration. This mus- cle is covered by the great pectoral, and partly at its insertion by the margin of the deltoid muscle, a few of its inferior fibres are covered only by the skin ; it lies ante- rior to the serratus magnus, axillary vessels and nerves. [Varieties. A third pectoral muscle, sometimes lies below this, arising from the first and second ribs, and inserted into the coracoid process. Sometimes a fasciculus arises from the first rib and passing beneath the lesser pectoral is inserted into the capsular ligament of the shoulder joint ; it is sometimes connected with the tendon of the coraco-brachial by a fleshy slip.] SUECLAVIUS, small and round, arises by a flat tendon from the cartilage of the first rib, external to the rhomboid or costo-clavicular ligament, soon becomes fleshy, and as- cending outwards and backwards, is inserted into the ex- ternal half of the inferior surface of the clavicle, extend- ing as far outwards as the space between the conoid and trapezoid ligaments. Use, to draw the clavicle and shoul- der forwards and downwards, also to elevate the first rib in inspiration, if the shoulder and clavicle be raised and fixed. This muscle is covered by the clavicle and great pectoral ; it lies anterior to the axillary vessels and nerves, which separate it from the first rib ; it is covered by a thin but strong aponeurosis, which is attached to the car- tilage of the rib, and to the clavicle and subclavian mus- cle, from which it passes downwards and outwards to the coracoid process, arching across the great vessels, and is then connected to that process, and to the tendon of the lesser pectoral ; this fascia is called by some the coraco- davicular ligament, by others the costo-coracoid ; it is some- times very strong, and from the manner in which it is ex- tended over the vessels, it renders it difficult to feel the pulsation of the axillary artery below the clavicle. [Variety. This muscle is sometimes double.] SERRATUS MAGNUS, thin and broad, particularly anterior- 70 DUBLIN DISSECTOR. ly, placed behind the pectoral muscles and the axillary vessels, and between the scapula and the ribs, arises by eight or nine fleshy slips, from the eight or nine superior ribs ; the fibres ascend obliquely backwards, and are in- serted between the subscapular, the rhomboid and levator anguli muscles into the base of the scapula, but particu- larly into the superior and inferior angles. Use, to draw the scapula forwards, particularly the inferior angle, and thus, by rotating this bone on its" axis, to raise the acromi- on process and the shoulder joint ; when the upper ex- tremity is fixed, this muscle can raise and draw outwards the ribs, so as to assist in inspiration. The serratus mag- nus lies on the ribs and intercostal muscles ; also on a portion of the serratus posticus ; external to it are the ax- illary vessels, the scapula and subscapular muscle; the trapezius, latissimus dorsi and rhomboid muscles lie be- hind it, and the pectoral muscles are anterior to it; an abundance of loose cellular membrane connected to its surface allows it to glide on the ribs, and also facilitates the movements of the scapula upon it. The four superior digitations lie behind those of the lesser pectoral, and the four inferior, which are only covered by the skin, indigi- tate with the origins of the external oblique. If the clavi- cle be separated from the sternum, and the scapula pulled from the side, this muscle will then become tense, and in this state it appears to consist of three portions, which diifer in structure and in form : the superior is a thick, short and strong fasciculus, somewhat square, passing from the two first ribs beneath the axillary vessels and brachi- al plexus, to the superior angle of the scapula ; its flat surface is directed upwards, and lies on a plane anterior to the next or middle division, which is very thin, consist- ing of but few fleshy fibres, connected together by an aponeurosis. This portion is of a triangular form, the apex attached to the third and fourth ribs, the base to the basis of the scapula, not exactly to the bone, but to a strong tendinous cord, which extends along this line from the superior to the inferior angle. The third, or inferior division of the serratus is the strongest and most exten- sive; it is radiated or triangular: the apex thick and fleshy, attached to the inferior angle of the scapula ; the base thin and expanded on the ribs. The serratus may be again examined when dissecting the muscle on the back of the trunk. [Variety. This muscle has sometimes ten or eleven origins.] INTEKCOSTALES, are twenty -two in number on each side, eleven external and eleven internal; the external com- DUBLIN DISSECTOR. 71 mence at the transverse processes of the dorsal vertebrae, arise from the inferior edge of each rib, descend in fasci- culi obliquely forwards, and are inserted into the external lip of the superior edge of the rib beneath, and terminate a little behind the costal extremity of the cartilages ; an aponeurosis, the fibres of which run in the same direction, supply their place as far as the sternum. The internal intercostal muscles take an opposite direction, and decussate the former : they commence at the sternum, and are dis- continued at the angles of the ribs ; they arise from the inner lip of the lower edge of each cartilage and rib, the fibres, paler and shorter than those of the external, de- scend obliquely backwards, and are inserted into the inner lip of the superior edge of the cartilage and rib beneath. Use, both laminae co-operate to raise the ribs, the first rib being fixed by the scaleni. The intercostal muscles, in elevating the ribs, also evert their lower edges, and twist them at their vertebral and sternal ends, and thus assist in inspiration by enlarging the chest transversely, and from before backwards. The internal layer lies on the pleura, and is separated from the external by the intercostal ves- sels and nerves ; the external layer is connected to the pleura only in the space between the angles of the ribs and the vertebrae. At the posterior extremity of the external intercostal muscles there are the following twelve small muscles, which, however, may be seen more fully when the muscles of the back have been dissected. LEVATORES COSTARTJM, arise narrow and tendinous from the extremity of each dorsal transverse process, descend obliquely outwards, and are inserted broad into the upper edge of the rib beneath, between its tubercle and angle ; their name denotes their use. They are parallel to, and frequently appear as a portion of the external intercostals ; the first levator is short, and arises from the last cervical vertebra ; the inferior increase in length and size. Behind the sternum are a pair of small muscles, triangu- lares sterni, which cannot be seen until this bone is re- moved ; we describe them now, although their dissection may be postponed until the cavity of the thorax has been opened. TRIANGULARIS STERNI, or STERNO-COSTALIS, arises from the posterior surface and edge of the lower part of the ster- num, and from the xiphoid cartilage ; the fibres ascend ob- liquely outwards, the inferior pass transversely inserted into the cartilages of the fourth, fifth, and sixth ribs. Use, to depress and draw backwards the cartilages of the ribs, so as to assist in expiration. These muscles lie on the pleurae, pericardium, and diaphragm, are covered by the 72 DUBLIN DISSECTOR. sternum, cartilages of the ribs, and mammary vessels. They antagonize the external intercostals, to whose fibres, however, they are parallel, but they arise from the more fixed, and are inserted into the more moveable part of the cartilage, and this also explains the cause of the external intercostals terminating at the ends of the ribs, and not con- tinuing as far forwards as the sternum. The mechanism of respiration shall be further considered when the dia- phram has been examined, (see dissection of it.) In con- nexion with the muscles of the thorax, the student should study the anatomy of the axilla. SECTION II. DISSECTION OF THE AXILLA. The Axilla is a conical cavity, the apex superiorly at the coracoid process and clavicle, the base below, between the pectoralis major, and the latissimus dorsi muscles, and formed by the skin and a thick fascia ; it is bounded an- teriorly by the great and lesser pectoral muscles, internal- ly by the serratus magnus and the ribs, externally by the scapula, subscapular muscle, and the upper part of the hu- merus, and posteriorly by the serratus, latissimus dorsi, and teres major muscles. This region contains several lymphatic ganglia, vessels and nerves, and a quantity of loose cellular and adipose tissue, which is continued from the neck beneath the clavicle, and often presents a watery reddish appearance. When the pectoral muscles have been divided, and some cellular membrane removed, the axillary vein first appears ; at the upper part of the axilla, this vessel is internal and anterior to the artery ; inferior- ly it is directly over this vessel, and more closely connect- ed to it than above ; this vein receives the cephalic vein, and several branches from the parietes of the thorax, and from the shoulder. The axillary artery may be next seen, taking an oblique course downwards and outwards through this space, and giving off thoracic branches from its inter- nal side ; and from its external, the subscapular and cir- cumflex arteries ; behind the artery, at the upper part of the axilla, the brachial plexus of nerves is seen ; as this de- scends it becomes more and more closely connected to it, and at the lower part of this cavity, the branches of the plexus have almost surrounded the artery. This plexus DUBLIN DISSECTOR. 73 rnay be seen dividing into several branches ; superiorly, it gives oft' the thoracic, supra, and subscapular ; and lower down it divides into the external and internal cutaneous, the median, ulnar, radial, or spiral, and articular or cir- cumflex. The general distribution of these branches will be noticed in the dissection of the upper extremity, and for their particular description, see Anatomy of the Nervous System. At the lower part of the axilla, the artery may be observed in general to lie between the two roots of the median nerve, with the external cutaneous to its outer or humeral side, and with the ulnar and internal cutaneous to its inner or thoracic side, while posterior to it are the musculo-spiral and articular nerves. The lymphatic gan- glia are connected to the axillary vessels by the small branches which supply them : several lie posterior to the edge of the pectoral muscle ; from these a chain continues up to the coracoid process, and are continued beneath the clavicle and the ganglia in the neck ; several also lie on the subscapular muscle, and some are scattered indifferent- ly through this space. Some of the conglobate ganglia of the axilla are very generally diseased, in cases of malig- nant affections of the breast, and must therefore be remov- ed by the surgeon, at the time of extirpating the latter. SECTION III. DISSECTION OF THE CAVITY OF THE THORAX. THE thorax is situated at the upper and anterior part of the trunk ; it contains the lungs, the organs of respiration ; the heart, the chief agent in the circulation of the blood, also several nerves and vessels passing to and from the heart, and through the cavity ; this region is bounded an- teriorly by the sternum arid costal cartilages, laterally by the ribs and intercostal muscles, posteriorly by the verte- brae and angles of the ribs, inferiorly by the diaphragm, superiorly by the several muscles connected to the clavi- cle, first rib and sternum, and by the different parts pass- ing into or out of the cavity. The thorax, viewed external- ly, presents a very different form before and after the up- per extremities are detached from it ; in the former state it appears of great transverse width above, and narrow be- low ; whereas in the latter condition, it is seen to be very contracted above and expanded below. The thorax may 74 DUBLIN DISSECTOR. oe compared to a section of a cone, the posterior fourth being removed, the three anterior parts retained and united to each other. The axis of the cavity is oblique from above downwards and forwards ; the base of the thorax is also oblique from before, backwards and downwards, and the apex on the contrary is oblique from behind, forwards and downwards ; hence the perpendicular diameter of the thorax is much greater posteriorly than it is behind the sternum. The apex of the thorax is somewhat truncated, and presents an oval opening, longer transversely than from before backwards ; this, the superior orifice of the tlio- rax, is bounded anteriorly by the upper edge of the ster- num and interclavicular ligament, posteriorly by the last cervical and first dorsal vertebrae, and laterally by the first rib : the several important parts which pass through this opening shall be noticed afterwards. The inferior cir- cumference of the thorax is five or six times more exten- sive than the superior ; it is bounded by the xiphoid, the last true and all the false costal cartilages, and by the last dorsal and first lumbar vertebras: its longer diameter is also transverse. Open the cavity by dividing the carti- lages of the ribs on each side of the sternum, and raising the latter from below upwards ; if we look under the ster- num as we thus slowly raise it, we perceive that space called anterior mediastinum to be gradually developed, from the right and left pleurae separating from each other as we tear the loose cellular membrane, which naturally con- nects the pleura and pericardium to the posterior surface of the bone : when the sternum is removed, this region is fully exposed ; it is described as being of a triangular form, the base, the sternum ; the sides, the pleurae, con- verging behind, so as nearly to touch each other ; the apex, the small portion of pericardium left uncovered by the pleuras ; naturally, however, all the parts within the tho- rax are so closely applied to the parietes, that no space or cavity of a defined form, like that assigned to the anterior mediastinum, can truly be said to exist.* The dissector, * For the purpose of examining the morbid appearances after death, the cavi- ties of the thorax and abdomen are generally opened at the same time ; an incision, carried from the top of the sternum to the symphisis pubis, through the integu- ments, muscles, and peritoneum, will bring the latter cavity into view; next let the skin and muscles covering the front of the thorax be turned back, which will expoae the cartilages connecting the ribs with the sternum ; immediately at their point of connexion with the bone, these are to be cut ; in doing this take care not to wound the viscera within. In some old subjects, where the cartilages of the ribs are in some degree ossified, a saw must be employed : all the cartilages, except those of the first rib, being di- vided, the sternum may be raised like the lid of a box, and a very convenient hinge is made by cutting the articulation between the first and second pieces of the sternum on the inside, opposite the second rib ; the figure of the thorax will llius be preserved, and a sufficient view be obtained of its contents). DUBLIN DISSECTOR. 75 nowever, may cause this space to appear more distinct by the following precaution : before you divide the cartilages, push your fingers from the abdomen behind the sternum, and break down the cellular connexions between it and the pleurae, then cut the cartilages very near the sternum, and raise the latter ; without this precaution before divi- ding the cartilages, the pleura, particularly the right, will be in almost every instance laid open, and so the appear- ance of the anterior mediastinum injured. This region in general inclines a little to the left side below, in conse- quence of the left pleura being more attached to the peri- cardium, which lies rather to the left of the middle line, whereas the right pleura is connected to the sternum in a vertical line : the anterior mediastinum is wider superior- ly and inferiorly than in the centre, hence some compare it to the letter X, and describe it as consisting of two trian- gular spaces, their apices joined in the centre, the base of one towards the neck, and that of the other towards the diaphragm : the superior portion contains the origins of the sterno-hyoid and thyroid muscles, and the remains of the thymus body ; inferiorly there is much loose cellular membrane, which leads from the neck to the abdominal muscles, also lymphatic ganglia, and close to the sternum are the mammary vessels, and the triangulares sterni mus- cles. Next examine the organs on each side of the thorax ; these are the lungs and their investing membranes the pleurae ; in almost all respects these organs are similar on the right and left side, and therefore either may be select- ed for examination ; for this purpose lay open one side, suppose the right, of the thorax, by sawing through the ribs about their centre, and removing their anterior por- tion ; the first rib may be left uninjured ; thus the cavity of the right pleura will be opened, its glistening surface seen, with the lung lying collapsed. The pleura are serous membranes, their internal surface is smooth, polished and free ; their external surface is connected by fine cellular membrane to the parietes of the thorax, and to the tissue of the lungs, over which they are reflected. That portion of each which invests the lungs is called pleura pulmonalis, and that which is connected to the parietes pleura parietalis or costalis ; the latter portion of the membrane is much more dense and strong than the former; each pleura is a shut sac, and contains only the serous vapour it ex- hales ; for although the lung appears within the cavity, it is yet really external to it or behind it ; internally each pleura presents one continuous surface, which can be traced throughout its whole extent; thus we can per- 76 DUBLIN DISSECTOR. ceive that the right pleura passes from the back of the sternum to form the side of the anterior mediastinum, and arriving at the forepart of the pericardium is continued along the side of that bag as far back as the root of the lung, whence it is reflected over the anterior surface of this organ, sinking into its fissures, and connecting all its lobules to each other ; having thus invested the whole lung, it arrives at the posterior surface of its root, from which it is reflected to the back part of the pericardium, where it approaches the opposite pleura, to which it is connected by cellular membrane ; thence it passes to the sides of the vertebrae, thus forming the side of the posterior mediasti- num (to be examined presently ;) the pleura then expands along the side of the spine, ascending as high as the trans- verse process of the sixth or seventh cervical vertebra, and descending to the diaphragm, the convex surface of which it covers ; on this muscle also it is reflected from the low- er edge of the root of the lung by a fold called ligamentum latum pulmonis, loose and triangular, the base towards the diaphragm, one side connected to the lung, and the oppo- site to the mediastinum; from the vertebra?, the pleura continues to pass outwards, lining the ribs and intercostal muscles, as far forwards as the side of the sternum, where the sac was opened, and the description commenced. The pleurae are of a conical form, the apex of each is in the neck, covered by the anterior scalenus and subclavian ar- tery, the base adheres to the diaphragm ; the right pleura is shorter but broader than the left, which is long and nar- row ; the liver on the right side and the heart on the left cause these differences to exist ; the apex of the right is often higher in the neck than that of the left. The two pleura have been compared to two bladders placed nearly parallel to each other, not having any communication, but touching each other along the mesial line ; this juxta-posi- tion of the two pleurae between the sternum and vertebrae forms a sort of partition between the right and left sides of the thorax ; this partition is called mediastinum ; it con- sists of course of two laminae, right and left, connected anteriorly to the sternum, posteriorly to the spine ; these laminae are separated from each other in three situations, in order to enclose certain organs, so that the mediastinum is divided into first, the anterior part, or anterior medias- tinum, which has been already examined ; second, into a middle part, or middle mediastinum, containing the heart and pericardium ; and third, into a posterior mediastinum, which lies in front of the vertebrae, and which the student may next examine. The posterior mediastinum extends in a vertical direction DUBLIN DISSECTOR. 77 from the third to the tenth dorsal vertebra, behind the pericar- dium and roots of the lungs, and in front of the spine ; to ob- tain a view of the parts contained in it, draw the right lung forward, and to the left side, and make a perpendicular division of the right pleura, between the root of the lung and the spine. This region is described as being of a tri- angular form, the base posteriorly, the pleurae forming its sides, and the pericardium its apex ; like the anterior medi- astinum, however, it has naturally no exact figure, the pleurse being folded round the organs which lie between them. In the posterior mediastinum we find the oesopha- gus and eighth pair of nerves, the thoracic duct, vena azy- gos, descending aorta, splanchnic nerves, several lympha- tic ganglia, and a considerable quantity of fine, loose cel- lular membrane ; the division of the trachea, also, is en- closed in this space, just at its commencement The oesoph- agus is anterior to the other parts in the posterior medias- tinum ; this tube having passed behind the left division of the trachea, enters this space, arid descends obliquely for- wards behind the pericardium and before the aorta ; above, it lies to the right side of this vessel, but below it is to the left ; in the lower part of its course it is surrounded by branches of the eighth pair of nerves, and enlarging a lit- tle, it perforates the fleshy part of the diaphragm, opposite the ninth or tenth dorsal vertebra, and joins the stomach. The eighth pair of nerves having passed behind the roots of the lungs, attach themselves to the oesophagus, and form by their branches a plexus around it, (the cesophageal plexus) ; the left nerve then descends on the fore, and the right on the back part of this tube to the stomach. The thoracic aorta enters this region about the fourth or fifth dorsal ver- tebra, and descends along the left side of the spine; about the eleventh or twelfth dorsal vertebra it passes between the crura of the diaphragm into the abdomen; in this course the aorta furnishes the following branches : two or three bronchial arteries, which go to the lungs, as many cesophageal branches, and nine or ten pair of intercostal arteries, whose name implies their destination. The vena azygos commences in the abdomen by a small branch from one of the superior lumbar veins, enters the thorax behind the right side of the posterior mediastinum, covered by the right pleura; and opposite the third or fourth dorsal vertebra it arches forwards over the root of the right lung, and opens into the superior vena cava, as that vessel is entering the pericardium. The vena azygos in this course receives the bronchial, oesophageal, and intercostal veins ; those of the left side often unite into one branch, which passing behind the 7* 78 DUBLIN DISSECTOK. aorta, joins opposite the sixth or seventh vertebra, the principal trunk on the right side. The thoracic duct also commences in the abdomen, on the second or third lumbar vertebra behind the aorta, in a sinus, called receptaculum chyli ; contracting in size it enters the posterior mediasti- num, along with, and to the right side of the aorta ; it as- scends between this vessel and the vena azygos, imbeo^ded in fat, and opposite to the fifth or sixth dorsal vertebra it attaches itself to the back of the oesophagus, runs obliquely along it, behind the arch of the aorta, to the left side, and ascends in the neck behind the left carotid artery and jugular vein, as high as the sixth cervical vertebra ; it then bends downwards and outwards, and enters the left sub- clavian, just before it joins the jugular vein. The coats of the thoracic duct are so fine and thin, that it is often diffi- cult to see or trace this vessel. (For a more particular de- scription of it, see the Anatomy of the Absorbent System.) The splanchnic nerves arise by four or five filaments from the dorsal ganglions of the sympathetic nerve ; the first is from the fifth or sixth ganglion, the rest arise in succession be- low it ; all unite and form the splanchnic nerves, which descend obliquely forwards on each side of the aorta, along with which they enter the abdomen, where each terminates in a large ganglion, termed semilunar; these two ganglions are joined together by numerous branches, which constitute the c&liac, or solar plexus, from which the greater number of the abdominal viscera are supplied with nerves. In the dissection of the posterior mediastinum, the sympathetic nerve is also seen on each side ; it does not lie in this space, but descends external to it, between the pleurae and the heads of the ribs ; opposite each intercostal space it forms a ganglion, from which some branches pass to join the dorsal spinal nerves, others to form the great splanch- nic ; and at the lower part of the thorax, two or three fila- ments often unite to form a small nerve, called lesser splanch- nic, which enters the abdomen behind or through the crura of the diaphragm, and joins the renal plexus of nerves. The sympathetic on each side enters the thorax close to the neck of the first rib, where it forms a large ganglion ; it passes from this cavity by a very small filament, between the crus of the diaphragm and the psoas magnus, into the abdomen, where it again enlarges considerably. (See the Anatomy of the Nervous System.) The division of the trachea, the last part of any importance connected with the posterior mediastinum, does not, strictly speaking, lie in this space, but like the heart and great vessels, it is in the middle mediastinum, or between the anterior and pos- terior,; this tube can be more conveniently examined after- DUBLIN DISSECTOR. 79 wards, when we are dissecting the parts which pass through the upper opening of the thorax. Next examine the lungs. The lungs are situated at either side of the spine, and when distended with air, as they constantly are during life, they so exactly fill each side of the thorax that the pleura? pulmonalis and costalis are always in such perfect apposi- tion, that there never can be any intermediate cavity ; they are of a conical figure, the apex, above, rises into the neck a little above the level of the first rib, and in general higher on the right than on the left side ; the base, below, concave, rests on the diaphragm : the external surface convex, and divided into two or three parts by a deep fissure ; the in- ternal slightly concave, and attached near its centre by the root to the heart and great vessels ; the posterior edge of each lung is thick, round and vertical ; the anterior is thin, irregular, oblique and shorter than the posterior ; that of the left side is in general notched opposite the apex of the heart. The right lung is broader but shorter than the left, the former consists most commonly of three lobes, the latter has only two. The great fissure of each lung de- scends obliquely forwards ; it commences behind the apex, and ends in front of the base ; it divides the substance of the lung, to a great depth into two lobes ; one is anterior and superior, and the other posterior and inferior ; the lat- ter is somewhat larger ; on the right side a small fissure leads from about the middle of the great one, forwards to the edge of the lung, and cuts off the middle lobe from the superior ; this fissure does not penetrate to the same depth as the great one does ; it is sometimes absent, and in some subjects it exists on the left as well as on the right side. The root of each lung is situated a little above the centre of the internal surface, and about two-thirds from the an- terior edge ; the phrenic nerve and a few filaments of the pneumogastric lie anterior to it, and the pulmonary plexus is posterior to it ; the fold called ligamentum latum is be- low it ; it consists of several vessels and nerves connected together by cellular tissue, and all enclosed between the laminae of the pleura ; dissect off this membrane from the forepart of the root, and we shall observe the two pul- monary veins inferior, but anterior to the pulmonary artery," which is immediately above and behind them ; pos- terior and superior to the artery is the bronchial tube ; a quantity of cellular tissue connects these vessels, and con- tains the bronchial arteries and veins, also several nerves, which are derived from the pulmonary plexus. In the root of the left lung the bronchial tube is rather inferior to the artery, but still posterior to it, as on the right side. 80 DUBLIN DISSECTOR. The lungs have a peculiar soft, emphysematous feel, and are so light as to float in water ; their colour is grey, in- terspersed with spots of dark blue or blackish tint : the younger the subject the redder the lungs will be found ; in the adult they are generally grey, and slightly streaked with dark lines ; in the old they are usually mottled with blue or black spots, which exist, not merely on the surface, but through their substance. The lungs are composed of the ramifications of the pulmonary arteries and veins, of the bronchial arteries and veins, of the pulmonary nerves, of lymphatic vessels and ganglia, and of the ramifications of the bronchial tubes, which end in numerous air cells ; these are collected at first in clusters, and joined by cellu- lar membrane into the lobules : these last are again united into larger masses by the pleura, so as to form lobes ; the air-cells are the terminations of the bronchial vessels ; they are globular, are lined by mucous membrane, and covered by a fibrous, or, as some suppose, a muscular lamina ; each bronchus divides into two branches, these again subdivide into two, and so on in binary order ; these canals increase in number, and diminish in size ; their final capillary branches end in small sacs or air-cells; these constitute the principal bulk of the lung : the larger bronchial tubes are composed of the same materials as the trachea, but in the smaller branches there is no cartilaginous structure. On their delicate parietes the fine capillaries of the pul- monary arteries and veins are spread, and here during life is effected that important change in the blood, from venous to arterial, which appears to be the great design of the function of respiration. The soft and yielding tissue of the lungs admits of the free entrance and rapid circulation of the air through their cells, all which become distended in the moment of inspiration ; in this act the lungs are wholly passive, the air distending them in the exact pro- portion with which the parietes of the chest are expanded; in expiration, the contraction of the thorax expels a great portion of the air from the cells, and thus the lungs be- come diminished in capacity ; in effecting this change, the elasticity, aided in all probability by the irritable or mus- cular energy of these organs, may assist the muscular and elastic power of the parietes of the chest. In expiration the air-cells are not wholly emptied ; no power can com- pletely discharge the air from lungs that have once breath- ed. See Anatomy of the Diaphragm. [There being no other organ of size, in the cavity of the thorax, besides the lungs and the heart, and the latter being on an average or the size of the fist of the individual, it is obvious that from an ex- ternal examination of the thorax, we can draw a sufficiently correct DUBLIN DISSECTOR. 81 inference as to the development of the lungs within ; neither is it the absolute size of the thorax, that indicates the best development of lungs, but its size as compared with the rest of the body and particu- larly the expansion of its antero-posterior diameter ; the volume of the right lung and its capacity are greater than that of the left, and this is in accordance with the fact, that the right bronchus is much larger than the left ; may not the difference in the size and length of the two bronchii (the left being nearly twice as long as the right, and but about half its calibre) and the smaller capacity of the left lung, have some relation with the fact, that this organ is more affected by tubucular disease, than the right. It is estimated that the capa- city of the lungs is such as to contain one hundred and forty-five cubic inches of air, and that by each act of expiration, thirty cubic inches are thrown off; we know of an individual who can displace one gallon of water by a single expiration, without great effort. The specific gravity of the lungs after inspiration is less than that of water, but in the foetus, and still born infants, it is greater than that of water, in which it sinks, a fact of much importance in legal medicine, and which in its practical application constitutes the hy- drostatic test; the absolute weight of the lungs, also differs at dif- ferent periods. In infants before respiration it is to the weight of the body, as one to sixty, after respiration, as one to thirty, owing proba- bly to the increased determination of blood through the pulmonary vessels ; in the adult subject of usual stature, it is said that the weight of the lungs, is about three pounds ; in disease it is often very much changed. The apex of the lung rises above the level of the first rib, sometimes an inch, and even two inches, and it has been suggested that the compression of the lungs by the edge of the first rib may produce irritation, and that this may be the reason that tubercles, are generally first developed in the apices.] The pleurse and lungs are the seat of many morbid changes ; the pleura, when inflamed, becomes thickened and vascular, and presents a deposit of lymph on the sur- face, which commonly causes an adhesion between the pleura costalis and pulmonalis to a very variable extent ; when these adhesions are recent, they are soft and easily broken, but when of long standing they become strong and resisting : adhesions of different extent and length are very common appearances. Portions of the pleura costalis are found sometimes converted into bony plates, and apparent- ly without having caused any inflammation or inconveni- ence. The cavity of each pleura is also the seat of effu- sion ; if of water or serum, it is named hydrothorax, if of pus, empyema ; the operation of paracentesis, or tapping, is frequently required in the latter case. The place usual- ly selected for this operation, is about midway in the fifth intercostal space, just in front of the digitations of the ser- ratus magnus muscle. The lungs are often found in a state of inflammation, (pneumonia), this is denoted by increased density, weight, 82 DUBLIN DISSECTOR. and colour, sometimes dark, sometimes very florid : the af- fected portion is often so heavy as to sink in water ; the dark colour from the gravitation of blood to a depending part, must not be confounded with that arising from dis- ease. Inflammation sometimes ends in abcess, which may open into the trachea or into the pleura, and so cause em- pyema. The lungs arc very subject to tubercles, which present great variety in size, from a pin's head to that of a walnut ; when small they are firm, when large they be- come soft, suppurate in the centre, and form abscesses or vomicse, which often communicate with the bronchial tubes. Tubercles are often found in the upper part of the left lung, when the remainder of both organs is healthy. The lungs are also occasionally the seat of cancerous and fun- goid tubercle and tumour. We shall next direct our at- tention to the pericardium and the heart. The pericardium is a strong fibro-serous membrane, in the form of a conical bag, whose base is below and apex above ; it is larger than the heart, which it encloses, to- gether with a portion of the great vessels connected to it, and over whose surface its internal or serous layer is re- flected : the external fibrous lamina is connected, inferior- ly, to the central division of the cordiform tendon of the diaphragm, and to some of its fleshy portion between the central and the left divisions of that tendon ; anteriorly to the pleurae, and to the parts contained in the anterior me- diastinum ; posteriorly, to the oesophagus and to the other parts in the posterior mediastinum ; superiorly, it is con- tinued along the outer coat of the great vessels, while the serous layer is reflected on these towards the heart. On each side it is in a similar manner connected to the pul- monary vessels ; the pleura and the phrenic nerve also are attached to it in this situation. The connexion between it and the tendon of the diaphragm, particularly towards its forepart, is very intimate ; in the adult they are almost in- separable, not so, however, in the foetus. Open this bag, and we shall see that it is lined throughout by a smooth serous membrane, which, if we trace to the superior part of the sac, we shall perceive to be reflected on the vena cava on the right side, on the aorta in the middle, and on the pulmonary artery on the left side ; on these three ves- sels it descends towards the heart : there is a longer por- tion of the aorta covered by the serous membrane, than of the vena cava or pulmonary artery, which two are nearly equal in this respect. The serous layer is reflected on the superior cava, opposite the entrance of the vena azygos ; as it descends along that vessel it nearly surrounds it, ex- cept a small portion of it posteriorly ; from the vena cava DUBLIN DISSECTOR. 83 it continues to the right auricle, which it covers anteriorly and on the right side ; from this it passes on the right pul- monary veins, covers these partially, and is thence reflect- ed to the fibrous layer ; from the lower part of the right auricle it is continued partly round the inferior cava, and from it also it is reflected to the fibrous layer. On the aorta the serous layer descends at first on the forepart, afterwards on its sides and back part, so as to encircle it ; near the heart it passes from it over the pulmonary artery, so as to connect these vessels to each other, leaving of course uncovered so much of each as are in apposition ; along these vessels the serous membrane descends to the ventricles, and having covered all the anterior surface of the heart, it turns round its apex, covers the posterior sur- face, and ascending on it as high as the upper edge of the left auricle, it is thence reflected on the fibrous layer in front of the posterior mediastinum ; from the left auricle also it extends to the left pulmonary veins, from which it is continued to the fibrous layer, and on this we can trace it in an uninterrupted course to that point, at which we commenced its description. The pericardium, by its fibrous lamina, is of use in fix- ing the heart in its situation, and strengthening its parie- tes, so as to resist over distention ; this tunic also, by its elasticity, may assist in the subsequent contraction of its cavities, while the serous layer being always lubricated by a fine fluid, facilitates the motion of the heart When the pericardium is fully opened, the right auricle, the two cavse, the appendix of the left auricle, the right or anterior ven- tricle, that small portion of the left which forms the apex of the heart, the aorta and pulmonary artery, also branch- es of the coronary vessels, ramifying on the anterior sur- face of the heart, all come into view. The pericardum is liable to inflammation : this is not a very common disease ; in this state it is crowded with mi- nute vessels, carrying florid blood ; it is also more pulpy and thicker than natural ; extra vasated coagulable lymph is found loosely connecting it to the heart ; this sometimes has a reticulated or lace-like appearance, and portions of it float in the serous fluid, which exists in the cavity. In some cases large quantities of pus are formed, without any appearance of ulceration, but always accompanied with a thickened state, and a deposition of coagulable lymph on the internal surface of the membrane. The presence of a small quantity of fluid in the pericardium after death, is not to be set down as a morbid appearance, or confounded with the disease called hydrops pericardii, as in every healthy body a few drachms of fluid are found 84 DUBLIN DISSECTOR. in the bag of the pericardium, arising from the condensa- tion of the natural exhalation, which exists in all serous cavities, or the oozing out of the blood from the contrac- tion of the heart after death. [The pericardium is sometimes entirely absent, but this is rare : it sometimes appears to be wanting in consequence of a complete ad- hesion to the surface of the heart. This organ is partially converted into bone, and one instance is recorded in which this conversion was complete. Three forms of effusion may coexist with pericarditis, serum, pus, and blood, and the quantity is sometimes very great, thus cases are recorded, of eight pounds of serum, of four quarts of pus, arid of one quart of blood, having been found. The false membrane of pericarditis varies in thickness from one line to nearly an inch ; inflammation of the fibrous lamina of the pericardium, occurs some- times by metastasis from other parts of the body.] The heart is placed obliquely between the lungs, the base of it is superior, posterior to the right side, and near to the spine, while the apex points towards the costal end of the cartilage of the sixth rib on the left side, and during life can be felt pulsating a little above and below this rib ; the heart is retained in situ by the pericardium, and by the great vessels; it is subject, however, to a slight change of position, according as that of the body is altered, as well as from the different states of inspiration and ex- piration. The heart consists of four cavities, two ventri- cles, and two auricles ; these the student may examine in that order or course which the blood pursues in passing through this organ. Suppose the two vense cavse pour their blood into the right auricle, so as to distend it, the parietes of this cavity then contract, and empty its con- tents into the right ventricle ; this next propels the blood into the pulmonary artery, the branches of which convey it through the lungs ; from these organs it is returned by the four pulmonary veins, two on each side, into the left auricle ; from this cavity it is forced into the left ventricle, which then propels it into the aorta, through whose branches it is conveyed to all parts of the body, whence it is again returned to the heart by the veins. The superior vena cava is seen descending obliquely forwards and in- wards within the pericardium, and joining the upper and back part of the right auricle. Of the inferior cava but a short portion is seen within the pericardium ; this vessel lies on a plane posterior to the superior cava, and passing obliquely upwards, backwards, and inwards, joins the lower and back part of the auricle. Between these two veins the right auricle is situated ; it is somewhat square, its posterior part, between the two cavse, is called the sinus; the anterior loose portion, the auricular appendix or process ; DUBLIN DISSECTOR. 85 the right auricle is connected inferiorly to the right ven- tricle, and partly rests on the diaphragm; on the right side it is free, and on the left it is connected to the left auricle ; lay open this cavity by a perpendicular incision from the superior down to within half an inch of the infe- rior cava, from the centre of this make a transverse cut towards the anterior part of the auricle, wash out the blood, and we may then observe at the back part of the sinus the openings of the two cav&, and between these a slight projection, tuberculum Loweri ; and in the auricular appendix the muscular fibres called musculi pectinati. We can also now perceive that the left or internal side of the auricle is formed by a thin sheet of membranous and muscular substance ; this is the septum auricularum ; on the inferior part of this we may observe a depression, the fossa ovalis, immediately above the inferior cava, and sur- rounded in part by a thick lip, named its annulus ; at the upper and deeper part of this fossa we frequently find a small oblique passage leading into the left auricle, its ob- liquity, however, prevents any communication taking Elace during life ; in the foetus before birth this was a ree opening, the foramen oxale, between the two auricles. Anterior to the opening of the inferior cava, we observe the semilunar fold of the lining membrane, the Eustachian valve: this valve is connected by its convex edge to the angle between the vein and auricle ; its concave edge is loose, and looks backwards and to the right side ; its su- perior cornu is connected to the anterior or the left limb of the fossa ovalis, and the inferior to the forepart of the vena cava ; this cornu is sometimes continued round that vessel to the posterior limb of the fossa ovalis : in the adult and old this valve is often reticulated and imperfect ; in the foetus it is generally more perfect and large, hence it is considered by many as being of use at that period in directing the blood from the inferior cava at once into the left auricle through the foramen ovale, and preventing its mixing with that from the superior cava. To the left side of the Eustachian valve, between it and the ventricle, is the orifice of the coronary vein, which is also partly covered by a semilunar fold of membrane, [the valve of Theoesius] that secures this opening against the re-entrance of the blood during the contraction of the auricle ; this valve also is often imperfect; on different parts of the auricle small orifices may be often seen, (foramina T^hebesii ;) these are probably the extremities of small veins. In the anterior part of the auricle we see the small cir- cular opening of the appendix, inferior to which, and op- posite the tuberculum Loweri, is the large orifice leading 8 86 DUBLIN DISSECTOR'. into the right ventricle ; this, the right auricula-ventricular' opening, is circular and surrounded by a dense white line, which has been erroneously described as the right tendon of the heart.- We may next examine the right ventricle : for this purpose open its cavity, by raising the anterior wall in the form of a flap from below, making one incision along its right side, and the other near the septum cordis. The right ventricle is triangular, its base is joined to the au- ricle, the apex is a little above the apex of the heart ; the right is separated from the left ventricle by a thick muscu- lar lamina (the septum cordis :) the parietes of this cavity are rendered very irregular internally by numerous mus- cular projections, the carnea column ; some of these are attached throughout their whole length, others are fixed by their extremities, and loose in their centre, and a third spe- cies are fixed by one end to the fleshy substance of the heart, by the other to thin tendinous cords [chordae tendinea] whicb are attached to the auricular valves ; the carneae co~ lumnee take various directions, and are all covered by the fine lining membrane of the heart. At the base of this ca- vity we observe the auricular' and arterial openings, the latter is superior,. anterior and to the left side of the former ; from the margin of the auricular opening a fold of the lining membrane descends into the ventricle, the inferior loose edge of which divides into three portions, each end- ing in a very irregularly notched margin, to which the chorda? tendineae are attached ; these are the tricuspid valves, one division is anterior ; the second is posterior, on- the septum cordis, and the third, which is the largest, is to the left side,- and separates the auricular from the arterial opening ; many of the tendinous threads are connected to the dorsum, as well as to the edge of these folds r and cross each other as they run to the ca Sarratus Magnus Anticus, Vide p. 69. Pectoralis Minor, " " 63. Subclavius, " " 69. Of these muscles the subclavius acts upon the clavicle only, the trapezius upon the clavicle and scapula, and the other five upon the scapula only ; their combined action is lo cause the scapula to rotate in such manner as to keep its glenoid cavity in contact with the head of the os brachii, so as to guard against dislocations of the shoulder joint. The omo-hyoid muscle is attached to the scapula but cannot effect its motions. SECOND CLASS, TWO MUSCLES. Pectoralis Major, Vide p. 67. Latissimus Dorsi, " " 97. These muscles act upon the os brachii to depress it, and are an- tagonists to most of the muscles on the region of the shoulder. The muscles of these two classes are situated on the anterior, lateral and posterior aspect of the trunk. The muscles on the region of the shoulder are six in number on each side, constituting a single class, and arranged in two groups. ONE CLASS, SIX MUSCLES. First Group, five Muscles. Deltoid, Vide p. 111. Supra Spinatus, Infra Spinatus, Teres Minor, Subscapularis, Vide p. 112. Vide p. 113. These muscles all act upon the upper end of the os brachii, except the deltoid and for the most part raise and abduct the arm, being an- tagonists to the pectoralis major, latissimus dorsi, and teres major. Second Group one Muscle. Teres Major, Vide p. 114. This antagonises the last group, and is a congener of the great DUBLIN DISSECTOR. 107 pectoral and latissimus dorsi, with which last it is inserted : they de- press and adduct the arm. The muscles of these two groups are situated for the most part on the surfaces and borders of the scapula. The muscles on the region of the arm are five in number on each side, arranged in two classes, the first, of one muscle acts upon the os brachii, the second of four acts upon the fore arm, and is arranged in two groups of two muscles each. FIRST CLASS, ONE MUSCLE. Coraco-Brachialis, Vide p. 114. This muscle lies upon the inner aspect of the arm which it raises, it is therefore a congener of the first group on the region of the shoulder. SECOND CLASS, TWO GROUPS. First Group, two Muscles. Biceps Flexor Cubiti, Vide p. 115. Brachialis Anticus, " " 116. These muscles flex the fore arm upon the arm, the first can also act upon the arm. Second Group, two Muscles. ^ Triceps Extensor Cubiti, Vide p. 117. Anconeus, " " 129. These muscles extend the fore arm upon the arm, and the first can also act upon the arm. The muscles of the first group are on the fore and inner part of the arm, those of the second upon the back and outer part. The muscles on the region of the fore arm are nine- teen in number on each side, arranged in three classes, the first of four muscles, rotates the radius upon the ulna. The second of six muscles, flexes and extends the hand upon the fore arm ; and the third of nine muscles, flexes and extends the fingers upon the hand, and can also move the hand upon the fore arm. The first class has two groups of two muscles each, one for supina- tion, the other for pronation. The second class has two groups of three muscles each, one for flexion the other for extension ; the third class has two groups one of three muscles, which act upon the fingers gene- rally, and is divided into two sets, another of six muscles, which act upon individual fingers, and is divided into three sets according to the fingers to which they are attached. FIRST CLASS, TWO GROUPS. First Group, two Muscles Supinator Radii Longus, Vide p, 127. Supinator Radii Brevis, " 129. Second Group, two Muscles. Pronator Radii Teres, Vide p. 122. Pronator Radii Quadratus, " " 126. These four muscles are all on the anterior aspect of the fore arm, 108 DUBLIN DISSECTOR. and are all inserted into the radius, the two first turn the dorsum of the hand to the ground, and the two last the palm. SECOND CLASS, TWO GROUPS. First Group, three Muscles. Flexor Carpi Radialis, } Flexor Carpi Ulnaris, > Vide p. 123. Flexor Carpi Medius, or Palmaris Longus, i Second Group, three Muscles. Extensor Carpi Radialis Longus, ) p.., , O7 Extensor Carpi Radialis Brevis, ( ae ?' J Extensor Carpi Ulnaris, " u 128. The first group is on the fore part, and the second on the posterior aspect of the fore arm. THIRD CLASS, TWO GROUPS. First Group, two sets. First set, two Muscles. Flexor Digitorum Sublimis Perforatus, Vide p. 124. Flexor Digitorum Profundus Perforans, " " 125. Second set, one Muscle. Extensor Digitorum Communis, Vide p. 128. These three are the common muscles of the fingers, the flexors are on the anterior, and the extensor on the posterior surface of the fore arm, hand, and fingers ; their primary action is to flex or extend the fingers, their secondary action, to flex or extend the hand. Second Group, three Sets. First Set, four Muscles. Flexor Longus Pollicis, Vide p. 126. Extensor Ossis Metacarpi Pollicis, i Extensor Primi Internodii Pollicis, Vide p. 130. Extensor Secundi Internodii Pollicis, S These, as appears from their names, are all long muscles of the thumb ; the first is on the anterior, the other three on the posterior and outer aspect of the fore arm ; these three will also abduct the hand. Second Set, one Muscle. Extensor Indicis, or Indicator, Vide p. 131. Third Set, one Muscle. Extensor Minimi Digiti. Vide p. 129. These two are on the posterior face of the fore arm, and can also assist in extending the hand. The muscles on the region of the hand are twenty in number on each side, arranged in two classes, in the first class are the twelve common muscles of the hand, in two groups ; in the second class are DUBLIN DISSECTOR. 109 eight muscles belonging to individual fingers, and arranged in three groups. FIRST CLASS, TWO GROUPS. First Group, one Muscle. Palmaris Brevis, Vide p. 121. This is a superficial cutaneous muscle, it arches the palm. Second Group, eleven Muscles. Lumbricales, four, Vide p. 132. Interossei, seven, " 133. These are deep seated muscles, the lumbricales and four of the in. terossei are to be seen from the palm of the hand, the other three in. terossei from the dorsum. SECOND CLASS, THREE GROUPS. First Group, four Muscles of the Thumb. Abductor Pollicis, ) , T ., Opponens Pollicis, \ Vlde ?' 13L Flexor Pollicis Brevis, ) 4i t Adductor Pollicis, $ * A2t Second Group, one Muscle of the Fore Finger. Abductor Indicis, Vide p. 133. Third Group, three Muscles of the Little Finger. Abductor Minimi Digiti, > Flexor Brevis Minimi Digiti, > Vide p. 133. Adductor Minimi Digiti, S If then, we review the muscles which act directly upon the supe- rior extremity, we shall find that on the region of the trunk there are nine muscles, on the region of the shoulder, six, on the region of the arm, five, on the region of the fore arm, nineteen, and on the region of the hand twenty, in all fifty-nine muscles for each extremity, or one hundred and eighteen for both ; the same number will be found in the classification of the muscles acting upon the inferior extremi- ties. Of the above number it will be seen that one hundred muscles are situated upon the superior extremities themselves. It may be proper to state here, that the muscles are subject to cer- tain morbid conditions of which one is preternatural contraction and rigidity ; this is more fully referred to in the chapter on the muscles of the lower extremities. Inflammation of the muscles is less common than of some other tissues, it may be either acute or chronic, it seldom runs into suppuration, mortification, or ulceration. The muscles are sometimes in a softened, sometimes an indurated, and occasionally even an ossified state ; this last affection is very rare, but a remark- able case is recorded in which most of the muscles of the extremities were converted into a solid mass of bone ; the muscles of the shoulder, loins, and calf, are most subject to this change. The muscles some- times undergo a fibrous or a fatty transformation, they may also be hypertrophied or atrophied ; tubercular, melanotic, schirrous, and en- 10 110 DUBLIN DISSECTOR, cephaloid, deposit are very rare. These organs are sometimes infested by parasitic animals ; many of the muscles are subject to congenital vareties, and those for the most part have their type in the muscles of different inferior animals.] DISSECTION OF THE MUSCLES OF THE SHOULDER AND ARM. DISSECT off the integuments from the shoulder and arm as low as the bend of the elbow ; beneath the skin and adipose substance is the brachial aponeurosis ; this is weak and imperfect in some situations as on the deltoid muscle ; in others it is strong and well marked, and it increases in strength as it descends ; it is connected posteriorly to the spine of the scapula, and to the infra-spinatus muscle ; in- ferior to this it receives an addition of fibres from the in- sertion of the deltoid ; internally it is in part continued along the vessels from the fascia "of the axilla, and in part also from the tendons of the great pectoral and latissimus dorsi ; it invests the whole arm, confining the muscles in their situation, and pressing them towards each other, par- ticularly along the inner side of the arm, so as to overlap the brachial vessels and nerves : as it descends it adheres to the lateral ridges of the humerus, which lead to the condyles ; these connexions are named inter-muscular liga- ments ; the internal is augmented by a prolongation of the coraco-brachialis tendon, and the external by fibres from the deltoid : the fascia of the fore arm we shall examine afterwards. Between the integuments and fascia of the arm we notice two cutaneous veins, the cephalic on the outer, and the basilic on the inner side ; the cephalic will be found hereafter to commence about the thumb, and to ascend along the radial side of the fore arm, and having passed the elbow joint, it is now seen continuing its course up the arm, at first on the outer side of the biceps, and afterwards between the deltoid and great pectoral muscles to the clavicle, beneath which it sinks to join the axillary vein; the cephalic vein is unaccompanied by nerves in its course up the arm, but in the dissection of the fore arm the external cutaneous nerve will be seen closely connected with it. The basilic vein will be found to commence about the little finger, to ascend along the ulnar side of the fore arm, and to pass over the elbow joint ; it is now seen con- tinuing its course on the inner side of the biceps, between the skin and fascia, and about the middle of the arm it perforates the latter, to join one of the deep brachial veins ; in some it continues superficial as high as the axilla, where it joins the axillary vein ; the basilic vein in the arm is accompanied by the cutaneous nerves of Wrisberg, which having escaped from the intercostal branches of the second DUBLIN DISSECTOR. Ill and third dorsal nerves, and passed across the axilla, are then distributed to the integuments on the inner side of the arm ; inferiorly the internal cutaneous branch of the brachial plexus accompanies this vein, and continues with it along the fore arm ; dissect off the fascia and cellular membrane from the muscles of the shoulder and arm. The muscles of the shoulder are six in number, viz. the deltoid, supra and infra-spinatus, teres minor and major, and sub-scapularis ; those of the arm are four in number, viz. the biceps, coraco-brachialis, brachialis anticus and triceps ; first examine the muscles of the shoulder. DELTOIDES, very thick and strong, triangular, arises ten- dinous from the lower edge of the spine of the scapula, and rather fleshy from the anterior edge of the acromion, and of the external third of the clavicle ; the fibres con- verge and descend obliquely, the posterior forwards, the anterior backwards, and the middle at first outwards, and then vertically downwards ; inserted tendinous into a rough surface, about two inches in extent, situated on the outer side of the humerus, and commencing just above its centre. Use, to abduct and raise the arm, the anterior fibres can also draw it forwards, the posterior backwards, and when the arm is by the side, these portions can rotate it in- wards or outwards. This muscle can also move the scapula on the arm when the latter is fixed, as in the case of a fall upon the hand or elbow, or in lifting a very heavy weight; under these circumstances this mus- cle sometimes co-operates with the great pectoral and latissimus dorsi, to dislocate the head of the humerus into the axilla. The deltoid is covered only by the skin, and a few fibres of the platysma; its origin corresponds to the insertion of the trapezius, with which it is often connected by aponeurotic fibres ; its insertion is surrounded by the origin of the brachialis anticus, and lies between the biceps 'and second head of the triceps ; its posterior mar- gin is thin, and sends off an aponeurosis to cover the in- fra-spinatus muscle; its anterior edge is separated from the great pectoral, by the cephalic vein, some cellular membrane, and a small artery. This muscle is fleshy on its external surface, coarse and rough, and composed of several distinct triangular fasciculi. Divide it transverse- ly, and reflect each portion, and we shall then see that its structure is very complex, and that its internal surface is much more tendinous; a large bursa is also seen beneath it ; this bursa extends under the acromion, and is expanded on the tendon of the supra-spinatus, and on the capsular ligament ; it allows the deltoid muscle and the exterior of the shoulder joint to glide easily against each other ; the 112 DUBLIN DISSECTOR. deltoid also covers the coracoid process, the muscles which are attached to it, all the small muscles connected to the capsular ligament, the insertion of the great pectoral, and the circumflex vessels and nerves. [Variety. A slip sometimes arises from the anterior edge of the scapula and joins the deltoid.] SUPRA-SPINATUS, fills the fossa of that name, and arises from all that portion of the scapula above its spine, which is engaged in forming this fossa, also from a strong fascia which covers the muscle ; the fibres pass forwards beneath the acromion process and triangular ligament, end in a tendon which glides over the neck of the scapula, (a bursa intervenes;) inserted into the upper and forepart of the great tuberosity of the humerus, into the most anterior of the three depressions which are marked on that surface. Use, to assist the deltoid in raising and abducting the arm, it also strengthens the capsular ligament, and draws it out of the angle, which is formed by the elevation of the arm, between the humerus and the glenoid cavity ; it also pres- ses the head of the humerus and glenoid cavity towards each other, prevents the head of the former from descend- ing out of the latter, and thus it becomes the antagonist to the pectoral, deltoid, and those other long muscles, which have a tendency to dislocate the head of the bone into the axilla. This muscle is covered by the trapezius, much cellular membrane and fat and by a strong aponeurosis ; its insertion is concealed by the deltoid, and the large bursa beneath that muscle, also by the acromion process and triangular ligament ; the tendon is inseparably con- nected to the eapsular ligament. INFRA-SPINATUS, is inferior to the last, flat and triangular ; arises fleshy from the inferior surface of the spine of the scapula, and from the dorsum of this bone, below this pro- cess, as low down as the posterior ridge on the inferior costa, but not from the rough surface on the inferior angle of the scapula ; it also arises from the aponeurosis which covers it ; the inferior fibres ascend obliquely forwards, the superior run horizontally; all converge, and are in- serted by a strong tendon, which covers and adheres to the outer part of the capsular ligament, into the middle of the external or greater tuberosity of the humerus, below the supra-spinatus. Use, to assist the superior part of the del- toid in raising the arm, and drawing it backwards, also in rotating it outwards : when the arm has been raised, its lower fibres can depress it ; it will also draw the capsular ligament out of the joint, and strengthen the articulation ; it is covered by the trapezius and deltoid ; but between these and the latissimus dorsi, a portion of it is superficial. DUBLIN DISSECTOR. 113 It lies on the bone, and the scapular vessels and nerves ; a large bursa lies between its tendon and the neck of the scapula. TERES MINOR, small and narrow, inseparably attached to the last muscle, along the lower edge of which it runs ; it arises from a depression between the two ridges on the in- ferior costa of the scapula, extending from the neck of the bone to within an inch and a half of its inferior angle, from the fascia which covers it, and from ligamentous septa, which enclose it; the fibres ascend obliquely forwards and outwards, cover and adhere to the capsule, and are in- serted below the infra-spinatus into the inferior depression on the great tuberosity of the humerus. Use, to co-operate with the last muscle. The origin of the teres minor is be- tween and overlapped by the infra-spinatus and teres ma- jor muscles ; its middle portion is superficial, and its in- sertion is covered by the deltoid ; it lies on the scapula, sub-scapular vessels, capsular ligament, and long head of the triceps, which last separates it from the teres major. SUB-SCAPULARIS, is situated on the inner side of the sca- pula, opposite to the three last described muscles, broad and triangular, the base behind, the apex before : it arises from all the surface and circumference of the sub-scapu- lar fossa, the fibres run in thick fasciculi up wards and for- wards, and all converge towards the neck of the scapula, over which they glide, beneath the coracoid process, and the muscles which are inserted into it ; they .end in a ten- don which is intimately united to the capsular ligament, and inserted into the internal or small tubercle of the hu- merus; this muscle is covered by the scapula and the muscles of the shoulder; its inferior edge is in contact with the teres major; its internal surface, which forms part of the axilla, is connected to the serratus magnus, and to the axillary vessels and nerves, by loose cellular mem- brane : a large bursa, very often communicating with the joint, lies between its tendon and the neck of the scapula, beneath the coracoid process: another smaller bursa is sometimes situated lower down, between the tendon and the -capsular ligament Use, this, which is the strongest of these capsular muscles, strengthens the inner side of the ar- ticulation, and guards against dislocation when the el- bow is suddenly drawn backwards and outwards. This muscle can depress and adduct the arm, draw it back- wards, and rotate it inwards, so as to turn the palm of the hand backwards, thus it antagonizes the infra-spinatus and teres-minor muscles. The deltoid and the four capsular musdfes, which have been just described, are of great use to the shoulder arti- 10* 114 DUBLIN DISSECTOR. culation ; the head of the humerus is so large, the glenoid cavity so superficial, and the capsular ligament so loose and long, that, but for these muscles, the bones could not remain in apposition ; hence, in cases of paralysis of the muscles of this region, the joint becomes elongated and flattened, and a partial dislocation exists ; in the dissect- ing-room also, if we divide all the muscles surrounding the capsule, and leave the latter uninjured, the bones will no longer be in contact ; these muscles, therefore, serve to strengthen the capsule, to keep the head of the humerus pressed against the glenoid cavity, and thus to counteract that tendency to dislocate the head of the bone, which the larger muscles of the limb frequently have, in consequence of their insertion being at such a distance from the centre of the joint, added to the anatomical imperfections in the latter already alluded to ; which imperfections, however, are much counterbalanced by the great mobility which the joint enjoys in consequence of this formation, by the numerous opposing muscles which serve to protect the ar- ticulation, and by the rotatory motion of which the scapula is allowed to partake. TERES MAJOR, long and flat, arises from a rough flat sur- face on the inferior angle of the scapula, below the infra- spinatus ; it forms a thick fleshy belly, which ascends for- wards and outwards to the inner side of the arm, and ends in a broad thin tendon, which is at first closely connected to the back of the tendon of the latissimus dorsi ; but near the humerus, a small bursa intervenes, and is inserted into the inner or posterior edge of the bicipital groove, behind the tendon of the latissimus, and in general, but not al- ways, extending lower down than it. Use, to rotate the hu- merus inwards, to adduct and draw it downwards and backwards ; also to draw forward the inferior angle of the scapula; whereby it not only assists the capsular muscles in retaining these two bones in apposition, but it also keeps the glenoid cavity opposed to the head of the hume- rus. The origin of this muscle is superficial, the latissi- mus dorsi sometimes overlaps it; it is here connected to the infra spinatus and teres minor ; from the latter the long head of the triceps afterwards separates it ; it passes anterior to this muscle, and assists the latissimus dorsi in forming the posterior fold of the axilla. The four muscles of the arm are the coraco-brachialis, biceps, and brachialis anticus in front, and the triceps be- hind. CORACO-BRACHIALIS arises tendinous and fleshy from the point of the coracoid process, and from the tendon of the short head of the biceps ; it descends obliquely forwards, DUBLIN DISSECTOR. 115 and is inserted, chiefly tendinous, into the internal side of the humerus, about the middle, and into the ridge leading to the internal condyle, by an aponeurosis, which forms the internal inter-muscular ligament, which is joined to the fascia of the arm. Use, to adduct, raise, and draw for- wards the arm ; also to rotate it outwards. The origin of this muscle cannot be separated from the short head of the biceps, but as it descends, it lies behind, and to the inner side of that muscle ; it is covered above by the deltoid and pectoral ; a small portion of it below is superficial, and is seen between the biceps and triceps ; its insertion is just below that of the teres major, and separates the brachialis anticus and posticus : the coraco-brachialis passes over the tendon of the subscapular, latissimus, and teres mus- cles ; the brachial artery and median nerve, at first lie to its inner side, but pass superficial to its insertion ; the belly of this muscle is generally, but not always, perforated by the external or musculo-cutaneous, or perforans Casse- rii nerve. BICEPS, is situated along the fore part of the humerus, and consists of two portions superiorly, the external or long, the internal or short ; the internal arises tendinous from the coracoid process, between the coraco-brachialis and triangular ligament ; it soon becomes fleshy, descends obliquely outwards, and a little above the middle of the humerus is united to the external or long head, which arises by a long tendon, from the upper part of the glenoid liga- ment of the scapula ; this tendon passes outwards through the joint over the head of the humerus, within the capsu- lar ligament, but external to the synovial membrane ; it then descends into the groove, between the two tuberosities of this bone, in which groove it is bound down by tendin- ous fibres, continued from the capsular ligament, and from the adjacent tendons ; the synovial membrane of the joint is reflected on this tendon at its origin, and is again reflect- ed from it inferiorly on the parietes of the groove, between the tendons of the great pectoral, latissimus dorsi, and teres major muscles ; thus, although the tendon passes through the cavity of the joint, it is, strictly speaking, external to the synovial membrane. A little below the middle of the humerus, these two portions of the biceps unite in a large fleshy belly, which, descending to within about an inch and a half of the elbow joint, ends in a flat tendon ; this sends off a process called the semi lunar fascia, to join the general aponeurosis of the fore arm, and then sinks below the joint into a triangular hollow between the supinator longus and pronator teres, and is inserted into the back part of the tubercle of the radius : a bursa intervenes between 116 DUBLIN DISSECTOR. this tendon and the anterior part of the tubercle, which is covered by cartilage ; the semilunar fascia which arises nar- row from the forepart of this tendon, opposite the bend of the elbow, passes upwards and inwards, expanding towards the internal condyle, to which, and to the muscles proceed- ing from it, some of its fibres are attached : the remaining become continuous with the aponeurosis of the fore arm. Use, to flex the fore arm, and make tense its fascia ; also to abduct and raise the arm. When the hand is prone, the first effect of the contraction of the biceps is to roll -the radius outwards, and turn the hand supine ; the long ten- don of the biceps, by passing over the head of the humer- us, prevents this bone being dislocated upwards and out- wards, as otherwise might occur, in consequence of a fall, or of a sudden muscular contraction : the biceps may also assist the coraco-brachialis, in rotating the scapula on the humerus, so as to depress the point of the shoulder. The long head of the biceps is concealed by the deltoid, supra- spinatus and capsular ligament; the short head by the great pectoral and deltoid : not unfrequently this muscle has another origin from the humerus below its head ; in some a fasciculus unites it to the coraco-brachialis, and in others to the brachialis anticus muscle, which lies be- hind it [This muscle is very liable to varieties; sometimes its two parts remain separate as far as the elbow, in a few rare cases it has had five heads.] The belly of the biceps is superficial, and lies on the brachialis anticus, so also is the tendon in its passage over the elbow joint ; the brachial artery descends along its in- ternal border, and somewhat overlapped by it, in the mid- dle and lower part of the arm. This muscle or its tendon will serve as a guide in the living subject, in case we are required to tie this vessel, but superiorly the coraco-brach- ialis intervenes ; the semilunar fascia is extended over the brachial artery and nerve, and affords them some, but not a constant protection, in performing venesection in the median basilic vein, which vein is superficial to this fas- cia, but parallel, and often so close to the artery as to ex- pose the latter to some danger in that operation- In dislo- cation, and in other injuries of the shoulder joint, the long tendon of the biceps is sometimes ruptured. BRACHIALIS ANTICUS, or EXTERNUS, improperly called by some INTERNUS, arises from the centre of the humerus by two fleshy slips, one on either side of the insertion of the deltoid, from the forepart of the bone down to the condy- les, and on each side as far as the inter-muscular liga- DUBLIN DISSECTOR. 117 ments ; the fibres descend converging, pass anterior to the elbow joint, adhere to the synovial membrane, and are in- serted by a strong tendon into the coronoid process of the ulna, and into a rough surface on this bone beneath that process. Use, to flex the fore arm, and in doing so it draws the synovial membrane out of the angle of the joint ; it also strengthens this articulation in its extended state, by press- ing the ulna against the humerus, and supporting the joint in front ; this muscle is covered by the biceps and by the brachial vessels and nerves ; external to the biceps it is superficial; its external head is the longer, and lies be- tween the deltoid and second head of the triceps ; the in- ternal separates the deltoid from the coraco-brachialis; the tendon passes deep into the hollow at the elbow, behind the tendon of the biceps, and is inserted on its internal side ; a fleshy fasciculus often unites this muscle and the biceps about the middle of the arm. [A fasciculus sometimes passes off to the supinator radii longus, and sometimes there is a second muscle but small, at the outer edge of the main muscle, having nearly the same attachments.] TRICEPS EXTENSOR CUBITI, covers the back of the humer- us, and extends from the scapula to the olecranon ; it con- sists superiorly of three portions, viz. the middle or long, the second or external, and the third or internal, or short head, or the brachialis interims or posticus. The long, or middle head, arises by a flat short tendon about an inch broad, from the lower part of the neck of the scapula, and from the anterior portion of the inferior costa ; it also adheres to the inferior part of the capsular ligament ; it soon ends in a large fleshy belly which de- scends along the back part of the humerus, that surface which is towards the bone continues tendinous for some distance : about the superior third of the arm it joins the second or external head, which arises immediately below the insertion of the teres minor by a narrow tendinous and fleshy slip, from a ridge on the outer side of the humerus commencing below the great tuberosity, and leading down to the external condyle ; it also arises from the bone be- hind this ridge, from the interrnuscular ligament, and from the external condyle, by a tendon which passes upwards and inwards, and joins the remainder of the muscle ; these inferior fibres are parallel to the anconseus ; the third, or short head, or brachialis internus, or posticus, improperly call- ed brachialis externus, arises narrow on the inside of the humerus, above its centre, commencing tendinous just be- low the insertion of the teres major, and continuing to arise from the ridge which leads to the internal condyle, 118 DUBLIN DISSECTOR. and from the internal intermuscular ligament; these three portions of the triceps unite above the middle of the arm, and descending along its posterior part, end in a flat broad tendon which consists of two laminae, a super- ficial and a deep ; the former is continued over the flat triangular surface of the olecranon into the fascia on the back part of the fore arm, the latter, which is stronger but narrower, is inserted into the olecranon process. Use, to extend the fore arm on the arm, and by its long portion to carry the arm backwards, and in some cases to adduct it; it also draws up the synovial membrane from be- tween the olecranon process and the humerus, and thus protects it from pressure in the extended state of the limb. The long head gives support to the inferior part of the capsular ligament of the shoulder, and so tends to pro- tect that joint against dislocation, in that situation where it would be most likely to occur. The sudden contraction of the triceps during life sometimes breaks off the ole- cranon process, and draws upwards the separated portion, of course the individual loses for some time the power of extending the fore arm ; the fractured piece, however, is prevented being separated to any considerable distance by the aponeurosis of the triceps which covers the olecranon, and which joins the fascia of the fore arm, and also by the inferior fibres of this muscle, which being connected to the* condyles, and having to ascend a little to the olecranon, tend to draw down its fractured portion. The first, or long head of the triceps, arises and descends between the two teres muscles ; the second, or outer head commences below the teres minor ; and the third, or the brachialis internus or posticus, below the teres major ; the long and the second head are covered above by the deltoid, the remainder of them is superficial ; the second lies external to the supina- tor longus and radial extensors of the carpus ; the third or internal head is also superficial, and lies between the bra- chialis anticus and coraco-brachialis anteriorly, and the long portion of the triceps posteriorly ; the ulnar nerve de- scends along this, and the radial or spiral separates it from the second or outer head ; a small bursa lies between the tendon, and the point of the olecranon, a larger one between the skin and the aponeurosis which covers that process ; this superficial bursa is peculiarly liable to inflammation, which is generally of an unhealthy character, in consequence of an injury, such as a fall upon the elbow producing a super- ficial lacerated wound. In the dissection of the muscles of the arm, we should notice the course of the brachial artery and of its principal branches, also the divisions of the axil- lary plexus of nerves : the cutaneous veins have been al- DUBLIN DISSECTOR. 119 ready noticed ; the deep veins accompany the arteries, tw*> to each. The brachial artery, which is the continuation of the sub- clavian and axillary, descends obliquely outwards, along the inner side, first of the coraco-brachialis, and afterwards of the biceps ; near the elbow it inclines forwards* and then sinks beneath the fascia of the biceps, and a little below the bend of the elbow it divides into the radial and ulnar arteries. In this course it is covered by the fascia and in- teguments, and overlapped a little by the biceps ; it is sur- rounded by a sheath of cellular membrane, which also contains the two vense comites; the internal cutaneous nerve lies superficial to it ; the median or brachial is also superficial to it above, and rather to its outer side ; about the middle of the arm, it crosses the artery, and inferiorly it is almost always to its ulnar or inner side. The ulnar nerve lies internal to the artery, and at some distance from it inferiorly ; the radial or spiral nerve is posterior to it, and separates it above from the triceps. In this course the artery passes over the tendons of the latissimus and teres, a small part of the triceps, the coraco-brachialis, and the brachialis anticus. The brachial artery gives off several muscular branches from its external side ; and from its in- ternal the superior profunda, which accompanies the spiral nerve round the back of the humerus to its external side ; the inferior profunda which descends along with the ulnar nerve towards the inner condyle, and the anastomotica magna, which runs towards the inner side of the elbow joint. See Anatomy of the Vascular System. The branches of the brachial plexus of nerves, which are met with in the dissection of the arm, are six in num- ber : first, the internal cutaneous, which has been already noticed ; second, the external cutaneous, or musculo cutane- ous, or perforans Casserii, pierces the coraco-brachialis muscle, descends obliquely outwards between the biceps and brachialis anticus, to which it sends several filaments, and at the anterior edge of the supinator longus it becomes cutaneous, descending along with the cephalic vein and its branches ; third, the median or brachial nerve accompanies the brachial artery to the bend of the elbow, and sinks be- neath the muscles of the fore arm, in the dissection of which the remainder of its course will be exposed : fourth, the ulnar nerve descends along the inner portion of the triceps, or the brachialis intern us, runs behind the inner condyle, and is then distributed to the muscles of the fore arm and hand ; fifth, the musculo-spiral, or radial nerve, de- scends between the second and third head of the triceps, and winds round the back part of the humerus, supplying 120 DUBLIN DISSECTOR. the triceps in its course ; it next runs spirally forwards to the forepart of the bone, between the supinator longus and brachialis anticus; it then descends over the forepart of the elbow joint to the muscles of the fore arm, where we shall trace it afterwards ; sixth, the circumflex, or articular nerve, accompanied by the posterior circumflex artery, passes out of the axilla between the long head of the triceps and the neck of the humerus, winds round the latter be- neath the deltoid muscle, to which its branches are distri- buted. See Anatomy of Nervous System. SECTION II. DISSECTION OF THE FORE ARM AND HAND. REMOVE the integuments from the front and back of the fore arm and hand, and the investing fascia will be exposed, together with the sub-cutaneous nerves and veins : the lat- ter may be noticed first. The basilic vein is seen to arise by small branches from the sides of the little finger, one of which is named sahatella ; it then ascends along the ulnar side of the fore arm, receiving in this course small branches from the front and back of the arm, and passing anterior to the internal condyle, it is joined by the median basilic ; it then ascends along the inner side of the arm, passes be- neath the fascia, and joins one of the deep brachial veins ; sometimes it continues in a superficial course to the axilla, and joins the axillary vein. The cephalic vein commences by several small branches about the thumb and back of the hand ; it ascends along the radial side of the fore arm, passes over the bend of the elbow, is joined by the median cephalic, and then ascends along the outside of the arm to the clavicle. The median vein arises by small branches from the forepart of the wrist, it ascends along the fore arm between the cephalic and basilic veins, and near the elbow divides into two or three branches : first, the median basilic, which ascends obliquely over the fascia of the biceps to join the basilic ; second, the median cephalic, which passes obliquely upwards and outwards, and joins the cephalic vein ; the third branch of the median, when present, sinks deep, and joins one of the deep veins. The internal cuta- neous nerve and its branches accompany the basilic vein, some passing anterior, others posterior to it ; the external cutaneous, or musculo-cutaneous, in general lies behind the cephalic vein at the bend of the elbow, its branches DUBLIN DISSECTOR. 121 afterwards twine around that vessel. The relation between the cutaneous nerves and veins is liable to great variety. The fascia of the fore arm is very strong, particularly on the posterior part ; it consists of tendinous fibres, which run in every direction, connected on either side to the con- dyles, and to the muscles which are attached to these ; it receives an addition from the biceps before, and from the triceps behind ; as it descends, it invests the limb so closely as to give it a certain form ; it sends septa between the dif- ferent muscles, which give attachment to several fibres, and it adheres very closely to the olecranon and to the ulna its whole length : inferiorly it is connected to the annular ligaments of the carpus. The annular ligaments of the wrist appear formed in part by this fascia, strengthened by proper transverse fibres ; the posterior is attached to the styloid process of the ulna internally, and to that of the radius externally ; it binds down the extensor tendons. The anterior annular ligament is much stronger ; it is at- tached to the unciform and pisiform bones internally, to the scaphoid and trapezium externally ; its upper edge is connected to the fascia of the fore arm, its lower to that of hand : this ligament, together with the carpus, forms a canal or ring for the passage of the flexor tendons. The integuments of the hand are thin posteriorly, and cover several cutaneous veins ; anteriorly they are dense, and the subjacent cellular tissue granulated and firm ; on the back of the hand a very thin aponeurosis exists, but ante- riorly, there is a remarkable, strong fascia, the palmar fascia: this is of a triangular form, commences narrow at the annular ligament, from which, and from the tendon of the palmaris longus, it arises ; it then expands over the palm of the hand, and near the fingers divides into four fasciculi, each of which is forked and inserted into either side of each of the sheaths of the flexor tendons, and into the capsular ligaments of the first phalanges ; transverse bands pass across these diverging fasciculi, and several fibres penetrate between the tendons, and join the meta, carpal bones and the interosseous muscles; a thin apo- neurosis, derived from the outer edge of the palmar fascia, covers the muscles of the thumb, and a similar one, those of the little finger. Attached to the palmar fascia is the following small cutaneous muscle. PALMARIS BREVIS, arises from the annular ligament and from the inner edge of the palmar fascia ; the fibres pass transversely inwards, and are inserted by scattered fibres into the integuments on the inner side of the palm of the hand. Use, to deepen the hollow of the palm of the hand by drawing the integuments towards the thumb. We have 122 DUBLIN DISSECTOR. no analogous muscle to this in the foot. We may now dis- sect off the fascia of the hand and fore arm, to expose the muscles; in some situations it is difficult and unnecessary to separate this from the muscular fibres ; beneath the palmar fascia we expose the superficial palmar arch of ves- sels and nerves passing across the flexor tendons and the lumbricales muscles. The muscles of the fore arm are so very numerous, that it will be found convenient to class them according to their situation and their use. One set of these muscles is em- ployed in bending the fore arm, wrist and fingers ; these are the flexors : a second, nearly allied to these, have the power of pronating the hand, that is, of rolling the radius across the ulna, so as to make the palm of the hand look downwards; these are the pronators : a third set, the exten- sors^ can extend the fore arm, hand, and fingers ; and a fourth, allied to these, the supinators, can turn the hand supine : that is, place the radius and ulna on the same plane, and make the palm of the hand look upwards. The pronators and flexors arise chiefly from the internal con- dyle, and from the inner or ulnar side of the fore arm ; each of these divisions may be arranged into a superficial and deep layer. The pronators and flexors arising from the inner side of the fore arm, are eight in number : five in the superficial layer, three in the deep ; the five superficial are, the prona- tor teres, flexor carpi radialis, palmaris longus, flexor digi- torurn sublimis, and flexor carpi ulnaris: the three deep muscles are the flexor digitorum profundus, flexor pollicis longus, and pronator quadratus. In the following descrip- tion of these muscles, the hand is supposed to be turned forwards, the radius externally, and the ulna internally. The muscles, which arise from the internal condyle of the humerus, are covered by the fascia of the biceps ; they cannot be separated from each other above, but have a common tendinous origin from the condyle, the fascia, and its septa, also from the ulna. PRONATOR RADII TERES, arises tendinous and fleshy from the anterior part of the internal condyle, from the fascia of the fore arm and its intermuscular septa ; also by a small tendon from the coronoid process of the ulna ; the median nerve separates these origins ; the fibres pass ob- liquely outwards over the radius, and are inserted, chiefly tendinous, into the outer and back part of the radius, about its centre. Use, to pronate the hand, by rolling the radius forwards and inwards over the ulna ; it is also a flexor of the fore arm : this is the most external of the muscles, aris- ing from the inner condyle ; it is superficial, except at its DUBLIN DISSECTOR. 123 insertion, which is covered by the supinator longus, and by the radial vessels ; it lies inferior to the supinator brevis : this muscle forms the internal boundary of the triangular hollow at the bend of the elbow, which contains the tendon of the biceps, the brachial nerve and vessels. [Variety. This muscle is sometimes double.] FLEXOR CARPI RADIALIS, arises narrow and tendinous from the inner condyle, and fleshy from the intermuscular septa ; it forms a thick belly, which lies very superficial, and ends in a prominent flat tendon ; this descends ob- liquely outwards, passes beneath the annular ligament, and is inserted into the base of the metacarpal bone of the index finger. Use, to bend the hand, and assist in prona- ting it ; this muscle is overlapped above by the pronator teres, and covered below by the annular ligament and by the muscles of the thumb, so that its insertion cannot be seen until the palm of the hand has been dissected ; it arises and descends at first between the pronator teres and palmaris longus, afterwards between this latter and the supinator longus, from which it is separated by the radial nerve and vessels : the radial edge of this tendon may serve as a guide, in cutting down on the radial artery in the liv- ing subject. PALMARIS LONGUS arises by a slender tendon from the inner condyle, and from the fascia of the fore arm ; forms a short belly, which ends in a flat tendon ; inserted near the root of the thumb into the annular ligament and palmar apo- neurosis. Use, to bend the hand and make tense the palmar fascia ; it descends between the flexor carpi radialis and ulna- ris, and lies on the flexor sublimis : it is sometimes wanting. [Sometimes its fleshy part is in the middle, and at other times its belly extends almost to the wrist.] FLEXOR CARPI ULNARIS, arises tendinous from the internal condyle, tendinous and fleshy from the inner side of the olecranon process ; the ulnar nerve and posterior ulnar re- current arteries separate these origins ; it also arises by a tendinous expansion from the inner edge of the ulna nearly its whole length, and from the fascia of the fore arm, the fibres pass obliquely forwards to a tendon which descends in front of the ulna, and which overlaps the ulnar nerve and vessels, and is inserted into the pisiform bone, and by a few ligamentous fibres into the base of the fifth metacarpal bone ; this insertion is also connected to the muscles of the little finger. Use, to flex the hand, and adduct it, particu- larly when assisted by the extensor carpi ulnaris : adduc- tion of the hand is not so limited as abduction, in conse- quence of the ulna being shorter below than the radius. 124 DUBLIN DISSECTOR. This muscle is superficial, and lies internal and rather pos- terior to the preceding muscles ; it descends between the flexor sublimis and extensor carpi ulnaris, and lies upon the flexor profundus ; the tendon passes over the annular ligament, and is connected to it by a tendinous slip, which also passes over the ulnar artery and nerve. FLEXOR DIGITORUM SUBLIMIS PERFORATUS, arises tendinous and fleshy from the internal condylc and internal lateral ligament ; tendinous from the coronoid process, and fleshy from the radius below its tubercle, internal to the pronator teres, and between the supinator breyis and flexor pollicis longus : it forms a large muscle, which ends in four ten- dons ; these descend, two anterior, for the middle and ring finger ; and two posterior, for the index and little finger ; they all pass beneath the annular ligament, and proceed along the palm of the hand, superficial to the deep flexor tendons, and beneath the palmar fascia : and at the first phalanx of each finger, or opposite the head of each me- tacarpal bone, each of these tendons becomes enclosed in a strong sheath, with one of the deep flexors ; this sheath is continued to the anterior extremity of the second pha- lanx. Near the end of the first phalanx, each of the su- perficial flexor tendons is split for the passage of the tendon of the deep flexor, which is continued on to the last or ungual phalanx ; while the divisions of each of the superficial tendons become somewhat twisted, that is, their inner or opposed edges are everted or folded out beneath the deep flexor, so as to lie nearer to the bone, and arc inserted into the anterior part of the second phalanx. Use, to flex the second joint of each finger on the hand, the hand on the fore arm, and the latter on the arm. The origin of this muscle is partly concealed by the three first described muscles, which arise from the internal condyle, and to which it is connected by the intermuscular septa ; inferiorly a portion of it is superficial between the flexor carpi ulnaris and palmaris longus. The tendons of this muscle are enveloped in a large bursa behind the annular ligament; this carpal bursa is connected anteriorly to the annular ligament, posteriorly to the carpus, is expanded around the superficial and deep flexor tendons, the medi- an nerve, and the tendon of the flexor pollicis longus, and ends above arid below in a cul dt sac, each end of which extends beyond the edges of the annular ligament. [This bursa is the seat of that affection called ganglion, in which the bursa forms a sort of hour glass tumour, one globe projecting into the palm of the hand, the other on the fore part of the wrist and the middle being constricted by the annular ligament ; on opening this tumom it may be found filled with serum, either thin and watery, or DUBLIN DISSECTOR. 125 very albuminous ; or with a substance resembling rice water ; or in more rare cases with a great number of small and distinct bodies like grains of barley. In the only case of this kind which we have met with, there was very little fluid, and none of the ordinary fluctuation, but an albuminous crepitus or grating sound, such as is sometimes heard in inflammation around joints after contusions : the rationale of cure in all these cases, is to effect an obliteration of the sac, by adhesive inflammation.] In the palm of the hand the tendons of the flexor subli- mis are covered by the integuments, palmar fascia, and the superficial palmar arch of vessels and nerves ; along the fingers each tendon is enclosed in a strong fibrous sheath, which is continued to the end of the second pha- lanx of each finger ; this sheath, together with the anterior- surface of the phalanges, forms a complete canal or tube, which, half fibrous and half osseous, is lined by a syno- vial membrane, which forms a cul de sac at either extremi- ty ; being reflected over the tendons it encloses, and form- ing several folds or frasna to connect these tendons to this canal : this sheath is weak, opposite each articulation, but is very strong on the phalanges ; its anterior extremi- ty is continuous with the insertion of the deep flexor tendon. [ Varieties. The tendon to the little finger is sometimes wanting, and supplied by the flexor profundus ; the portion of the muscle going to the fore finger, is sometimes so distinct, as to appear like a sepa. rate muscle.] Divide the flexor sublimis and carpi radialis, and the three deep muscles will be partially exposed, namely, the flexor digitoruna profundus, flexor pollicis longus, and nearly concealed by .these, the pronator quadratus. FLEXOR DIGITORUM PROFUNDUS PERFORANS, arises fleshy from three superior fourths of the anterior surface of the ulna, and from the internal half of the interosseous liga- ment ; it sometimes receives a small slip from the radius below its tubercle ; it forms a thick muscle which descends along the middle and ulnar side of the fore arm, and ends in four flat tendons ; these pass beneath the annular liga- ment, enter the ligamentous sheaths on the fingers, pass through the slits in the superficial flexor tendons, and are inserted into the last phalanx of each finger. Use, to bend the last phalanx and to co-operate with the superficial flexor muscle in bending the other phalanges and the wrist ; this muscle is covered by those of the superficial layer, which have been described ; the ulnar vessels, the median and ulnar nerves also descend along it ; and it covers the ulna, the interosseous ligament and vessels, the 11* 126 DUBLIN DISSECTOR. pronator quadratus and the carpus, and on each finger its tendon is superficial to that of the flexor sublimis. [Variety. There is sometimes a fasciculus uniting the tendon going to the fore finger, with the flexor longus pollicis.] FLEXOR POLLICIS LONGUS, arises from the forepart of the radius, commencing narrow just below its tubercle, and from the interosseous membrane, to within about two inches of the carpus, it also very frequently arises by a long and narrow tendinous and fleshy slip from the coro- noid process ; this at first looks like a distinct muscle ; all the fibres descend obliquely forwards to a tendon, which passes beneath the annular ligament, and then runs out- wards between the two portions of the short flexor, and the two sesamoid tubercles at the extremity of the meta- carpal bone ; it next enters a strong ligamentous sheath, and is confined by it as far as the last phalanx of the thumb, into the middle of which it is inserted. Use, to flex and adduct the different joints of the thumb upon the hand, and the latter upon the fore arm. This muscle is covered by the flexor sublimis and radialis, and by the radial ves- sels, and inferiorly by the annular ligament, it descends along the radial side of the flexor profundus. PRONATOR QUADRATUS, is exposed by separating the flexor pollicis and profundus ; it is a small square muscle situat- ed just above the carpus, and arises tendinous and fleshy from the inferior fifth of the anterior surface of the ulna ; the fibres pass transversely outwards, descend a little, and are inserted into the anterior part of the inferior fourth of the radius. Use, to roll the radius over the ulna, and so to pronate the hand : this muscle is covered by the ten- dons of the preceding, and by the ulnar and radial vessels, and it lies on the interosseous ligament, the radius and the ulna. [Variety. This muscle is sometimes, though rarely, wanting.] The muscles which are situated on the outer and back part of the fore arm are supinators and extensors, and are also arranged into two layers, a superficial and deep ; the superficial consists of seven, namely, supinator radii lon- gus, extensor carpi radialis longus, and brevis, extensor digitorum communis, extensor minimi digiti, extensor car- pi ulnaris and anconrcus ; these muscles arise more dis- tinctly than those on the internal side of the arm : some of them however, particularly those on the ba.ck part, are closely connected to each other, arising in common from the external condyle of the humerus, from the posterior surface of the radius and ulna, the intermuscular ligaments DUBLIN DISSECTOR. 127 and the fascia, which is partly derived from the tendon of the triceps. SUPINATOR RADII LONGUS, forms the prominence along the outer and anterior part of the fore arm, arises tendinous and fleshy from the external ridge of the humerus, com- mencing a little below the deltoid and continuing to with- in about two inches of the outer condyle; it also arises from the intermuscular ligament, which separates it from the second or outer head of the triceps, between which and the brachialis anticus this muscle is situated. The supi- nator longus descends along the outer and anterior part of the elbow, and about the middle of the fore arm ends in a flat tendon, which descends along the radius, and is inserted into a rough surface on the outside of that bone, near its styloid process. Use, to roll the radius backwards, so as to make the hand look supine ; it can also bend the elbow joint. This muscle is superficial ; it passes over the ex- tensor carpi radialis longus above, the tendon of the pro- nator teres in the middle, and the radius inferiorly ; its ten- don descends at first between the pronator teres and ex- tensor radialis longus, afterwards between the latter and that of the flexor carpi radialis ; at its insertion it is cross- ed by the extensor tendons of the thumb. This muscle and its tendon overlap the radial nerve and vessels ; its ulnar edge, therefore, will serve as a guide to the latter, in case we are required, during life, to expose them, in order to tie a ligature around the radial artery. EXTENSOR CARPI RADIALIS LONGUS, arises tendinous and fleshy from the ridge on the external side of the humerus, between the supinator longus and the external condyle ; it forms a thick short belly which passes over the outside of the joint, ends in a flat tendon, which descends along the outer and back part of the radius, runs through a groove on its lower extremity, and passing over the wrist joint, is inserted into the back part of the carpal end of the metacarpal bone of the index finger, nearly opposite to that of the flexor carpi radialis. Use, it extends the wrist, bends the hand backwards, and abducts it a little ; it may also assist in bending the elbow joint ; its belly is covered by the last described muscle, but projects behind it ; the tendon descends behind that of the supinator longus, and passes beneath the extensors of the thumb and the annular ligament ; it covers the supinator brevis and the following muscle. [Varieties. This muscle is also sometimes inserted into the third metacarpal bone by a distinct slip ; sometimes this muscle and the next, are so blended, as to appear common.] EXTENSOR CARPI RADIALIS BREVIS, arises tendinous and 128 DUBLIN DISSECTOR. fleshy from the inferior and posterior part of the external condyle, and from the external lateral ligament, forms a thick belly, which descends along the back part of the ra- dius, ends in a flat tendon, which runs through the same groove as the tendon of the last muscle, internal to which it lies ; passes also beneath the annular ligament, and is inserted into the carpal extremity of the third metacarpal bone, or that of the middle finger. Use, similar to that of the last ; it is covered superiorly by the last described muscle, and by the supinator longus, and below by the tendons of the extensor muscles of the thumb, and by that of the last muscle, and by the skin ; it covers the supinator brevis and the insertion of the pronator teres. EXTENSOR DIGJTORUM COMMUNIS, is situated more towards the back part of the fore arm than the last described mus- cles ; it arises in common with the last, and with the exten- sor minimi digiti from the external condyle, the fascia, and its intermuscular processes, also from the ulna; it de- scends along the back of the fore arm, and about the mid- dle of the latter ends in four tendons, which pass under the annular ligament in a groove in the radius, extend along the back of the hand, expanding as they approach the four fingers, into all the phalanges of which they are inserted by a tendinous expansion. Use, to extend all the joints of the fingers, also the carpus ; this muscle arises between the extensor carpi radialis brevis and extensor minimi digiti ; it descends superficially between these, and over the supi- nator brevis and extensors of the thumb ; on the back of the hand the tendons are connected to each other by cross slips ; that which goes to the ring finger is the largest ; all the tendons, as they approach the base of the first phalanx, become thick but narrow ; afterwards they enlarge and are joined by the tendons of the lumbricales and interos- sei ; at the articulation of the first and second phalanx each divides into three bands ; the middle one is inserted into the posterior surface of the second phalanx ; the late- ral pass along the sides of this articulation ; they after- wards converge and unite in a flat tendon, which is insert- ed into the base of the last or third phalanx. The back part of all the fingers is covered, as far as the last phalanx, by a tendinous expansion, derived from these tendons, and from those of the lumbricales and interossei muscles. [ Variety. This muscle sometimes sends a double tendon to the little finger.] EXTENSOR CARPI ULNARIS is very superficial, arises ten- dinous and fleshy between the extensor minimi digiti and anconoeus, from the external condyle, fascia and intermus- DUBLIN* DISSECTOR. 129 cular septa ; descends obliquely inwards, between the flexor ulnaris and extensor minimi digiti, towards the ulna, and receives an addition from it ; it ends in a strong ten- don, which runs through a groove on the back of the ulna, beneath the annular ligament, and is inserted into the car- pal end of the fifth metacarpal bone. Use, to extend the hand and bend it backwards : also to adduct it, that is, flex it laterally towards the ulna. [Variety. Sometimes the tendon of this muscle is united to the extensor muscle of the little finger.] ANCONJEUS, small, triangular, and placed at the outer side of the olecranon, beneath the skin ; arises narrow and fleshy from the posterior and inferior part of the external condyle and lateral ligament, forms a thick triangular mass, which adheres to the synovial membrane and de- scends obliquely inwards, to be inserted into the external surface of the olecranon, and about the superior fifth of the posterior surface of the ulna. Use, to extend the fore arm on the arm, and to raise the synovial membrane out of the articulation ; this muscle is partly covered by the tendon and aponeurosis of the triceps ; the remainder of it is superficial ; it is situated between the olecranon and the extensor carpi ulnaris ; it often appears as a continua- tion of the triceps ; it covers a portion of the elbow joint and of the supinator brevis. EXTENSOR MINIMI DIGITI, vel AURICULAKIS, arises in com- mon with the extensor communis, and descends between it and the extensor carpi ulnaris ; it forms a small fleshy belly, which descends very obliquely inwards, and ends in a slender tendon ; this passes through a separate groove in the radius, and also through a distinct division of the an- nular ligament, in which situation it is frequently found divided into two, which continue in contact, and afterwards unite ; this tendon becomes attached to the fourth tendon of the extensor communis, and is inserted along with it into the posterior part of the phalanges of the little finger. Use, to assist the extensor communis, and to extend and abduct the little finger independent of the others. The deep muscles in this situation are five in number, they will be exposed by removing the superficial layer ; they consist of the supinator radii brevis, three extensors of the thumb, and the indicator. SUPINATOR RADII BREVIS, short and flat, surrounds the upper part of the radius, arises from the external condyle, external lateral and coronary ligaments, and from a ridge on the outer side of the ulna, which commences below its lesser sigmoid cavity ; the fibres adhere to the capsular 130 DUBLIN DISSECTOR. ligament, and descend obliquely outwards and forwards round the upper part of the radius, and are inserted into the upper third of the external and anterior surface of this bone, from above its tubercle down to the insertion of the pronator teres. Use, to turn the radius outwards, so as to make the hand look supine ; it can also assist in extending the fore arm. This muscle nearly surrounds the upper part of the radius, it is covered by the supinator longus, the radial extensors of the carpus, and the extensor digito- rum communis externally ; by the anconseus and extensor ulnaris posteriorly ; and anteriorly by the radial nerve and vessels, and by the brachialis and biceps ; it partly sur- rounds the humeral and ulnar articulations of the radius ; its anterior edge is notched above for the insertion of the biceps, and is overlapped by the pronator teres below. [Variety. This muscle is sometimes double.] EXTENSOR Ossis METACARPI POLLICIS, or ABDUCTOR POL- LICIS LONGUS, arises fleshy from the middle of the posterior part of the ulna, below the anconseus, also from the inter- osseous ligament and posterior surface of the radius below the supinator brevis ; it descends outwards and forwards, and ends in a tendon, which passes through a groove on the outside of the lower end of the radius, runs by the side of the carpus, and is inserted in general by two tendons, one into the os trapezium, and the other into the upper and back part of the metacarpal bone of the thumb. Use, to extend the first joint of the thumb, and separate it from the fingers; it also extends the wrist, and abducts the hand ; it can also assist in supination. The origin of this muscle is concealed by the extensor communis and carpi ulnaris ; the tendon is superficial and passes over the ten- dons of the radial extensors of the carpus, also over the radial vessels. [Variety. This muscle is sometimes double.] EXTENSOR PRIMI INTERNODII POLLICIS, or EXTENSOR MINOR, arises from the back part of the ulna, below its middle, and from the interosseous ligament and radius; it descends along the ulnar side of the last muscle ; its tendon passes through the same groove in the radius, is bound down by the same portion of the annular ligament, and is insert- ed into the posterior part of the first phalanx; a small slip is often continued on to the second phalanx. Use, to ex- tend the second joint of the thumb, and to assist the last described muscle ; its connexions are also similar. [Varieties. This muscle is sometimes an appendage of the last, and sometimes confounded with the next muscle.] EXTENSOR SECUNDI INTERNODII POLLICIS, or EXTENSOR DUBLIN DISSECTOR. 131 MAJOR, arises from the posterior surface of the ulna above its centre, and from the interosseous membrane ; its belly overlaps the two former muscles, its tendon passes along a distinct groove in the radius, runs over the outer side of the wrist, the metacarpal bone and first phalanx of the thumb, and is inserted into the posterior part of the second or last phalanx. Use, to extend the last phalanx of the thumb upon the first, and to assist the former muscles in extending and supinating the hand. The tendon of this muscle is separated from the two former, on the outer and back part of the wrist, by a considerable interval, in which we perceive the tendons of the radial extensors of the car- pus, and the radial artery ; the relations of this muscle in other respects are nearly similar to those of the other ex- tensors of the thumb. EXTENSOR INDICIS, or INDICATOR, arises from the middle of the posterior surface of the ulna and interosseous mem- brane ; its tendon passes under the annular ligament along with those of the common extensor, is attached to the ra- dial side of that tendon which belongs to the fore finger, and is inserted along with it into its second and third pha- langes. Use, it assists the common extensor, or produces the extension of the fore finger alone, as in pointing. This muscle is concealed by the extensor communis and ulna- ris, lies to the ulnar side of the extensor pollicis major, and its tendon passes under those of the common extensor, to which it is sometimes connected by a tendinous slip. [Varieties. This muscle sometimes has two bellies, sometimes it is double, and the second muscle goes to the middle finger.] Next dissect the muscles of the hand ; first, those in the palm, which consist, externally, of the muscles of the thumb ; internally, of those of the little finger, and in the middle of the lumbricales superficially, and the anterior interosssei, deep seated. The short muscles of the thumb are five in number, viz. the abductor, opponens, flexor brevis, adductor pollicis, and abductor indicis. ABDUCTOR POLLICIS, arises broad and thin from the ante- rior part of the annular ligament, os naviculare and trap- ezium, inserted into the outside of the base of the first pha- lanx, and by an expansion into the back of both phalan- ges ; its name implies its use, to separate the thumb from the fingers ; it lies superficial, and is most external of these small muscles, which form the ball of the thumb. OPPONENS POLLICIS, or FLEXOR Ossis METACARPI, arises from the annular ligament and os naviculare ; inserted into the anterior extremity of the metacarpal bone of the thumb. 132 DUBLIN DISSECTOR. Use, to approximate the thumb to the fingers ; it is internal to and partly overlapped by the last muscle ; it lies on a part of the annular ligament, and of the following muscle, from which it is separated with difficulty. FLEXOR POLLICIS BREVIS, consists of two portions, between which is the tendon of the flexor longus ; one head, the ex- ternal or anterior, arises from the inside of the annular liga- ment, and from the trapezium and scaphoid bones, passes outwards, and is inserted into the external sesamoid bone or cartilage and base of the first phalanx of the thumb ; the second, or internal or posterior, arises from the os magnum, and the base of the metacarpal bone of the middle finger ; it also passes outwards, distinct from the other at first, but afterwards united to it, and is inserted into the internal sesa- moid bone, and base of the first phalanx. Use, to flex the first phalanx and metacarpal bone on the carpus ; this mus- cle is concealed by the two former, and by the first lum- bricalis ; it covers the two first interossei muscles, and the tendon of the flexor carpi radialis ; its outer edge is con- nected to the opponens pollicis, and the internal to the ad- ductor. ADDUCTOR POLLICIS, triangular and broad, arises fleshy from three-fourths of the anterior surface of the third meta- carpal bone, or that of the middle finger, the fibres pass out- wards over the second metacarpal bone, and converging are inserted into the inner side of the root of the first phalanx of the thumb, along with part of the last muscle ; its name denotes its use. This muscle at its origin is covered ante- riorly by the deep flexor tendons and by the lumbricales ; its insertion is covered by the following muscle, which may be best seen from behind. ABDUCTOR INDICIS, is also triangular, is situated between the thumb and index finger, and is best seen on the poste- rior aspect of the hand. Arises tendinous and fleshy from the metacarpal bone of the fore finger, and from one-half of that of the thumb ; its fibres extend obliquely inwards and forwards, end in a tendon which passes by the outer side of the first joint of the fore finger, and is inserted into the outer side of the base of its first phalanx. Use, to sepa- rate the fore finger from the others, or to adduct the thumb. This muscle is superficial posteriorly ; anteriorly it is cover- ed by that last described ; the radial artery passes between its two heads or origins : this muscle is similar to, and may be regarded as one of the posterior interossei ; like these also, its insertion joins that of the common extensor tendon. In the middle of the palm of the hand are seen four small muscles. LUMBRICALES, are four in number; they arise from the DUBLIN DISSECTOR. 133 outer or radial side of the tendons of the flexor profundus, near the carpus, a little beyond the annular ligament ; they each form a small fleshy belly, which ends in a tendon ; this runs along the radial side of the. finger, joins the tendon of the corresponding interosseous muscle, and is inserted about the middle of the first phalanx into the tendinous ex- pansion which covers the back part of each finger. Use, to assist in bending the first joint of the finger ; they cannot do so unless the flexors are tense ; they can also adduct and abduct the fingers, and when the common extensor muscle is in action, they may assist in extending them ; these small muscles are covered by the superficial flexor tendons, pal- mar vessels and nerves : the first is the largest, the fourth the smallest; the two middle run nearly parallel, but the internal and external diverge : the tendons of the lumbri- cales frequently divide into two portions ; one of these will be inserted into the first phalanx, the other into the posterior tendinous expansion. Variety. One of these muscles is sometimes wanting : sometimes one or more is double, and then the accessory is sent to the ulnar side of the adjoining finger.] On the inner side of the palm of the hand are the short muscles of the little finger, which are three in number. ABDUCTOR MINIMI DIGITI, arises fleshy from the annular ligament and from the pisiform bone ; its fibres run along the ulnar side of the metacarpal bone, and are inserted ten- dinous into the ulnar side of the first phalanx ; its name im- plies its use ; it is superficial ; a few fibres of the palmaris only cover it ; its origin is partly continous with the inser- tion of the flexor carpi ulnaris. FLEXOR BREVIS MINIMI DIGITI, arises from the annular liga^ ment and unciform bone, inserted by a round tendon into the base of the first phalanx of the little finger. Use, to flex and adduct the little finger ; it lies to the radial side of the last muscle, along with which it is inserted. [Variety. This muscle is sometimes wanting.] ADDUCTOR, or OPPONENS MINIMI DIGITI, arises along with, but internal to the last, and overlapped by it, and is inserted into all the metacarpal bone of this finger : its name de- notes its use. When all the flexor and extensor tendons have been re- moved, we observe the intervals between the metacarpal bones to be filled by muscular fibres, which are called the interosseous muscles ; they are divided into two planes, a pos- terior and an anterior. The INTEROSSEI ANTICI, or INTERNI or PALM ARES, are four in number ; they arise from the sides of the metacarpal bones, and are inserted into the first pha- 12 134 DUBLIN DISSECTOR. langes, and into the tendinous expansion which covers the dorsum of each finger : the first or prior, or externus indicis, arises from the radial side of the second metacarpal bone^ and is inserted into the external side of the first phalanx of the fore finger. Use, to adduct the fore finger ; the second or posterior, or internus, or adductor indicis, arises from the ulnar side of the second metacarpal bone, and is inserted into the inner side of the first phalanx of the fore finger ; third or prior, or externus or adductor annularis, arises from the radial side of the fourth metacarpal bone, and is inserted into the external side of the first phalanx of the ring finger. Use, to draw the ring finger towards the thumb ; the fourth, or interosseous minimi digiti, arises from the radial side of the fifth metacarpal bone, and is inserted into the outside of the first phalanx of the little finger. Use, to draw the little finger towards the thumb. The POSTERIOR or DORSAL INTEROSSEI, are seen on the back part of the hand ; they are longer than the anterior ; they each arise by two sets of fibres from the opposed sides of two metacarpal bones, and are inserted into the base of the first phalanx of each finger, and into the posterior ten- dinous expansion ; the first, or prior, or externus medii, arises from the second and third metacarpal bones, fills the space between these two, and is inserted into the outer side of the base of the first phalanx of the middle finger. Use, to draw the middle finger towards the thumb ; the second or internus medii is situated between the metacarpal bones of the mid- dle and ring finger, and is inserted into the inner side of the first phalanx of the middle finger. Use, to draw the middle towards the ring finger ; the third, or externus annularis, is between the fourth and fifth metacarpal bones ; and is in- serted into the inner side of the ring finger. Use, to draw the ring finger inwards. All these muscles can also extend the fingers. Some consider the dorsal interossei as four in number, making the abductor indicis the first of this class. In the dissection of the fore arm and hand we meet with the branches of the brachial artery, with their accompany- ing veins ; also branches of the brachial plexus of nerves : the cutaneous veins have been already noticed. The bra- chial artery, when it arrives at the bend of the elbow, di- vides into its radial and ulnar branches. The radial artery descends from the elbow obliquely outwards, to the styloid process of the radius, passes over the outer side of the carpus, and then between the metacarpal bones of the thumb, and of the fore finger, where it divides into three branches, radialis indicis, magna pollicis, and palmaris profunda : the radial artery at first lies between the pronator teres and supinator longus; afterwards between the supinator and DUBLIN DISSECTOR. 135 flexor carpi radialis : it then winds round the carpus, over the external lateral ligament, and beneath the extensor ten- dons of the thumb ; in the fore arm it is only overlapped above by the supinator longus ; in the rest of its course it is superficial ; it is accompanied by two veins, and by the radial branch of the musculo-spiral nerve, which lies to its outer side. The radial artery gives off, first, the recurrent branch, which ascends in front of the external condyle, to supply the muscles attached there, and to inosculate with the supe- rior prof un da ; second, in its course down the fore arm, seve- ral muscular branches: third, near the wrist, the superfi- cialis volee, which passes to the small muscles of the thumb, and communicates with the superficial palmar artery ; fourth and fifth, branches to the fore and back part of the carpus : and between the thumb and index finger it divides into its three last branches ; the magna pollicis subdivides, and sup- plies the sides of the thumb ; the radialis indicis, in like manner, supplies the fore finger ; and the palmaris profunda passes beneath all the flexor tendons across the four meta- carpal bones, forms the deep palmar arch, and then joins a branch from the ulnar artery. The ulnar artery is larger than the radial : it descends obliquely inwards, beneath the superficial flexors and pronators, and lies on the flexor pro- fundus ; it passes over the annular ligament into the palm of the hand, and there divides into a superficial and deep branch ; this vessel is covered above by several muscles, in- fer iorly it is superficial, and lies between the tendon of the flexor sublimis and flexor carpi ulnaris ; it is attended by its two veins, and in the inferior two-thirds of the fore arm by the ulnar nerve, which always lies to its ulnar side ; near the wrist this nerve is somewhat behind the artery. The ulnar artery sends off', first and second, its recurrent branches, the anterior, small, ascends in front of the inter- nal condyle, the posterior, large, passes behind that condyle and joins the inferior profunda ; third, the interosseous ar- tery, which passing backwards, divides into its posterior and anterior branch ; the posterior passes through the upper part of the interosseous space, and ascends in the substance of the ancoriseus [by its recurrent branch, after which it de- scends upon the back of the fore arm, as far as the wrist ;] the anterior interosseous descends between and beneath the flexor profundus and flexor pollicis as far as the pronator quadratus, where it terminates ; fourth, muscular branches ; fifth and sixth, branches, to the back and front of the carpus ; and in the palm of the hand it terminates in the deep and superficial branch ; the former sinks between the muscles of the little finger, to join the deep palmar arch ; the superficial runs across the flexor tendons, forming the 136 DUBLIN DISSECTOR. superficial arch, from the convex side of which, the long digital arteries arise ; these supply the three inner fingers. (See Vascular System.) In addition to the cutaneous nerves already noticed, we find the median, ulnar and musculo-spiral descending in the fore arm ; the median nerve passes between the heads of the pronator teres, and descends beneath the flexor sublimis, giv- ing off the anterior interosseous nerve, and branches to the muscles of the fore arm ; it passes beneath the annular liga- ment, appears superficial in the palm of the hand near the thumb, and sends off digital branches, which accompany the digital arteries to all the fingers, except the little and the ulnar side of the ring finger. The ulnar ?ierve winds round behind the internal condyle, between the heads of the flexor carpi ulnaris, and descends along the internal side of the ulnar artery to the hand, where it terminates, by dividing into a small superficial and a large deep branch. The mus- culo-spiral or radial nerve is seen beneath the supinator lon- gus, descending along the outer side of the radial artery, and supplying the adjacent muscles ; near the elbow it gives off the posterior interosseous nerve, and a little below the middle of the fore-arm it passes beneath the tendon of the supinator, and becomes cutaneous, being distributed to the integuments of the thumb and back of the hand. (See Anatomy of the Nervous System.) CHAPTER VI. DISSECTION OF THE ABDOMEN. SECTION I. OF THE MUSCLES ON THE ANTERIOR AND LATERAL PARTS OF THE ABDOMEN, DIVIDE the integuments from the sternum to the pelvis, from the crest of the ilium on each side to the umbilicus, also from this point upwards and outwards on each side over the cartilages of the ninth and tenth ribs, as high as midway between the axilla and the border of the thorax ; dissect off the flaps ; the subcutaneous cellular membrane will be found dense and strong, so as to have received the name of superficial fascia ; this may be removed along DUBLIN DISSECTOR. 137 with the integuments from the superior and lateral parts of the abdomen, but inferiorly and anteriorly it may be suffered to remain for further examination, a knowledge of its structure and connexions being of practical impor- tance in the disease of hernia. The superficial fascia is continued from the surface of the thorax, over the ab- dominal muscles; weak and thin above, it increases in density as it descends ; from the abdomen it extends on either side over Poupart's ligament to the thigh, which it invests, and in the centre over the organs of generation : in the male a process of it passes round the spermatic cord on each side, descends into the scrotum, and is con- tinuous with the fascia of the perineeum, and from the li- nea alba a thick portion runs to the dorsum of the penis, invests this organ, and serves as a suspensory ligament to it. In the female it is loaded with fat in this situation, and descends into the labia. As this fascia passes over Pou- part's ligament, it is connected to it, through the medium of a thin transparent but strong membrane, which ascends from the fascia lata of the thigh, and is soon lost on the abdominal muscles ; to this the superficial fascia is attach- ed, so as to give the latter the appearance of adhering to Poupart's ligament, although it really is not so. This structure is sometimes called Scarpa's fascia, as that writer has described it under the name of the "Aponeurosis of the fascia lata," it is very unequally developed in different subjects ; some of the inguinal ganglia separate this from the superficial fascia, so also does a femoral hernia, in its ascent on the surface of the abdomen. About an inch below this ligament, in the groin, the superficial adheres intimately to the fascia lata; in this situation ifee former is very thick and laminated, forming capsules for the in- guinal lymphatic ganglia, and is connected to the fascia lata, -by vessels and nerves which perforate the latter in their course to and from these ganglia, the superficial fas- cia and integuments ; the fascia lata here also is very weak, and rather cellular^ so that the superficial and deep fascias are continuous or identified in this situation ; soon afterwards, however, they become distinct. The super- ficial fascia is thinner along the sides than it is on the forepart of the abdomen : its cutaneous surface is cellular, and closely connected to the integuments, particularly in the median line ; its posterior surface is more compact and smooth ; several blood-vessels ramify between the skin and this membrane ; three set on each side, viz. the external circumflex ilii, external epigastric, and external pudic ar- teries ; these all arise in the groin, from the fermoral ar- tery, or from some of its branches, and ascend over Pou- 12* 138 DUBLIN DISSECTOR. part's ligament: the first ramifies towards the anterior spinous process of the ilium; the second, which is the largest of the three, ascends towards the umbilicus ; and, the third passes transversely towards the pubis ; these several arteries supply the integuments, and inosculate with the deep seated vessels of the same name ; they are each ac- companied by one or two veins, which are often found re- markably tortuous. The superficial fascia supports and connects the fleshy and tendinous fasciculi of the abdomi- nal muscles ; it also possesses a good deal of elasticity, which assists these muscles in the contraction of the parie- tes of the abdomen, Remove the integuments and fascia from the surface of the abdominal muscles, and continue the dissection as far back as within two or three inches of the spine. In dissecting the external oblique muscle at its upper and anterior part, care must be taken not to raise its aponeurosis, which is so thin, as it passes over the anterior part of the thorax, that it may be mistaken for condensed cellular membrane. In order to expose the external obli- que muscle, make its fibres tense by putting a block under the loins, and dissect in a line nearly parallel to its fibres ; to clean the posterior portion, the subject should be turned a little to the opposite side. The abdominal muscles con- sist of five pair, viz. obliqui externi, and interni, transver- sales, recti, and pyramidales. [These muscles are found in three layers, in the first one pair, in the second three .pair, and in the third one pair. FIRST LAYER, OWE PAIR. ^Obliquus Externus, or Descendens. SECOND LAYER, THREE PAIR. Obliquus Internus, or Ascendens. Rectus Abdominis. Pyramidalis. THIRD LAYER, ONE PAIR. Transversalis Abdominis.] OBLIQUUS EXTERNUS, or DESCENDENS, broad, thin, and somewhat square, extends over the anterior and lateral parts of the abdomen, fleshy above and behind, tendinous before and below ; it arises by eight or nine triangular fleshy slips, sometimes there are only seven, from the low- er edges and external surface of the eight or nine inferior ribs, at a little distance from their cartilages; the five su- perior indigitate with corresponding portions of the serra- tus magnus ; and the three inferior with those of the latis- simus dorsi, by which they are a little overlapped. The superior fibres are thin, aponeurotic, and weak, and pass 1WBLIN DISSECTOR. 139 horizontally inwards; a tendinous and fleshy slip often connects this portion to the great pectoral muscle: the middle are the longest, and descend obliquely forwards and inwards ; the posterior are strong and fleshy, and de- scend almost vertically: the superior and middle fibres end in a broad tendon, which commences at a little dis- tance external to the linea semilunaris ; this tendon is con- tinued over the forepart of the abdomen, covers the rectus muscle, and is so broad inferiorly, as when taken with its fellow to extend from one .spine of the ilium to that of the opposite side,; it is very strong inferiorly, but so very thin above, where it covers the thoracic portion of the rectus, that the inexperienced dissector often removes it along with the integuments. The external oblique is inserted ten- dinous into the ensiforni cartilage, linea alba, pubis, Pou- part's ligament, which is formed by this tendon, and into the anterior superior spinous process of the ilium, also tendinous and fleshy into the outer edge of the two anterior thirds of the orest of the ilium. Use, to depress the ribs, and compress the abdominal viscera, so as to assist in ex- piration, and in the evacuation of the urine and faeces. When both muscles act, they can bend the trunk for- wards ; if one only act, it will bend it to that side, and it may also rotate it to the opposite side. This muscle is covered by the skin and superficial fascia, its posterior border is sometimes overlapped by the latissimus dorsi ; in some cases, however, these muscles do not meet, and a small part of the internal oblique is seen in the triangular space between them. [Variety. This muscle maybe defective at different points, thus giving a tendency to the formation of ventral herniae.J On the dissected tendons of this pair of muscles, we may remark the following particulars ; the linea alba and um- bilicus, linese semilwmres, linese transversse, the external abdominal or inguinal rings, arid Pouparf s ligament on each side. The linea alba is a dense ligamentous cord, ex- tending from the ensiform cartilage to the upper part of the symphisis pubis ; it is formed by the intimate union, or by the crossing of the tendinous fibres of the two ob- lique and transverse muscles of opposite sides ; its great- est breadth is at the umbilicus, from this to the pubis it de- creases ; its superior portion is much broader than its in- ferior : the integuments are more closely connected to this line, than they are at either side ; hence the more fat the subject, the more indented will the skin appear along it. About the centre of the linea alba is the umbilicus; this, in the foetus, was a foramen, through which were transmitted 140 DUBLIN DISSECTOR. the umbilical vein from the mother, and the umbilical ar- teries and the urachus from the child ; before the integu- ments were removed, this spot appeared depressed, partic- ularly if the subject have been very fat ; it now projects, and seems formed of dense, cicatrized cellular tissue, sur- rounded by, and connected to the adjacent tendinous fibres. Umbilical hernia occurs in the infant through this open- ing, but in the adult in its immediate vicinity. The linea alba may be regarded as the continuation of the sternum, it serves as a fixed point for the oblique and transverse muscles on either side, also as a ligament to connect the thorax to the pelvis, and to support the former when bending the trunk backwards, so as to resist or pre- vent too forcible extension of the spine. In the inferior part of this line the following operations may be perform- ed : puncturing the bladder in retention of urine : para- centesis, or tapping of the abdomen, in ascites ; and the high operation for lithotomy. The inferior fourth or fifth part of the linea alba is sometimes deficient, as also a portion of the muscles on each side ; so that the urinary bladder is superficial, and constantly exposed : in such cases the anterior part of this viscus also is usually wanting, and therefore its cav- ity and the orifices of the ureters can be perceived during life. The linea semilunarls extends from the tuberosity of the pubis on each side upwards and outwards, about four in- ches from the linea alba, towards the cartilages of the eighth and ninth ribs ; it appears white, and somewhat de- pressed, and is formed by the tendon of the internal ob- lique, dividing at the edge of the rectus into two layers, to enclose this muscle in a sort of sheath. In the living sub- ject this line may be traced by taking the point midway between the umbilicus and the anterior superior spinous process of the ilium, and from it drawing one line towards the tuberosity or spine of the pubis, and another towards the cartilage of the ninth rib. The operation of tapping ovarian dropsy, should always be performed here : and this situation is also selected by some as the best for per- forming paracentesis in case of ascites. In this last men- tioned disease, however, this line is not exactly midway between the umbilicus and spine of the ilium, but half an inch nearer the latter. The linea transrerscc are three or four on each side, they cross the rectus muscle from the linea alba to the linea semilunaris ; they are tendinous intersections of that mus- cle, particularly of its anterior part, which adhere so inti- mately to its sheath, as to give to the latter this indented DUBLIN DISSECTOR. 141 appearance. They are much better marked in some than in others ; during life they are very distinct, when the ab- dominal muscles are in strong action. These lines will be again noticed in the dissection of the rectus. Between the linea alba and semilunaris on each side many small holes are often to be observed in the tendon of the external ob- lique : these are only for the transmission of small vessels and nerves : they are generally of a square form, and are much larger and more numerous in some than in others. External and superior to the pubis on each side we may always remark the opening called the external inguinal, or abdominal ring, transmitting in the rnale subject the sper- matic vessels and cremaster muscle, and in the female the round ligament of the uterus. This opening is of a trian- gular form, the base at the pubis, the apex is superior and external ; the sides are called the pillars of the ring, one of which is superior, internal, and anterior ; the other, or Poupart's ligament, is inferior, external, and posterior ; the first, or superior pillar, is broad, and inserted into the sym- physis and into the opposite pubis ; some fibres are con- tinuous with the fascia lata of the opposite thigh ; this pil- lar decussates with that of the opposite side, on the fore- part of the pubis, and both send fibres to the dorsum of the penis ; the inferior pillar is the internal or pubic portion of Poupart's ligament ; the apex of this opening is round- ed by a series of fibres, which serve to connect the pillars to each other. These fibres arise from Poupart's ligament at a little distance from the spine of the ilium, pass in curved lines upwards and inwards across the upper part of the ring, and are lost on the surface of the tendon ; they serve, by preventing the separation of the sides of the ring, to protect this part of the abdomen against a protrusion of its contents. These fibres are in some cases so closely connected, as to merit the name of a fascia (the intercolum- nal fascia) ; this, in old cases of hernia, has been found of great strength, and prolonged for some distance on the hernial sac, and intimately connected with the cremaster muscle (fascia spermatica) ; it is this fascia, or these in- tercolumnal bands, that obscure this opening in many cases, and deprive it of that defined figure usually men- tioned by writers, or delineated in plates. The tendon of the external oblique is alone concerned in the formation of the external abdominal ring, there being no correspond- ing deficiency in the internal oblique or transverse mus- cles ; the spermatic cord, or round ligament, must there- fore take an oblique course to arrive at this opening ; this will be seen in the next stage of the dissection. Pouparfs or Fallopius' ligament^ or the crural arch, is the 142 DUBLIN DISSECTOR. inferior thickened edge of the tendon of the external ob- lique ; it is very strong, and when the lower extremity is extended, and the foot and toes everted, it appears very tense ; if we consider it as a distinct ligament, it may be described as having an attachment to, or as arising from the anterior superior spinous process of the ilium, and thence descending obliquely forwards and inwards to the pubis, into which it is inserted by two attachments, one an- teriorly into the tuborosity or spine ; the other posteriorly in- to the linea innominata of the pubis, or the commencement of the linea ilio-pectinea : the first or iliac end of Poupart's ligament is broad and continuous above with the tendon of the oblique, and below with the fascia lata ; the an- terior portion of the pubal end, or the second insertion, is distinct and round, and can be felt through the skin ; it lies behind the cord, and is connected to that portion of the fascia lata which covers the adductor muscles ; the pos- terior pubal attachment, or the third insertion, also called Gimbernaut's ligament, is broad and thin, and lies superior, posterior and external to the former ; it may be seen by raising the cord out of the external ring, and everting Pou- part's ligament a little ; it is of a triangular form, the apex is anterior towards the tuberosity or spine of the pubis ; the base is external and posterior, somewhat crescentic, looking towards the femoral vessels ; to it some fibres from the outer or iliac part of the fascia lata are attached, so as to elongate it in this direction ; this third insertion of Pou- part's ligament forms the internal boundary of the femoral ring, and is therefore concerned in the anatomy of femoral hernia, as will be seen hereafter. Poupart's ligament owes much of its strength to its connexion with the fascia lata of the thigh, as may be seen at present, also to its at- tachment to the fascioe transversalis and iliaca, which will be exposed in a future stage of the dissection. Poupart's ligament is of use in strengthening the inferior part of the abdomen, and affording a fixed point of attachment to the deeper muscles and to the different aponeuroses ; it also protects the great femoral vessels and nerves in their pas- sage from the abdomen to the thigh, and its third insertion partly fills up the internal portion of the crural arch. From this third insertion, and from the pubis, a band of fibres may be observed to pass upwards and inwards be- hind the superior pillar of the ring towards the linea alba ; these assume in general, a triangular shape, and have received the name of the triangular ligament or fascia ; the base is inferiorly at the linea ileo-pectinea ; the apex is superior and internal towards the linea alba, and is conti- nuous \vrth the external oblique tendon of the opposite DUBLIN DISSECTOR. 143 side : this fascia serves to protect the abdomen in this re gion. Raise the external oblique, by dissecting off its ser- rated origins from the ribs, detach also its insertion from the crest of the ilium, and from the internal oblique mus- cle, cleaning, at the same time, the surface of the latter, throw the external oblique towards the opposite side, sepa- rating it as far forwards as its connexions will permit, that is, about half an inch internal to the linea semilunaris; divide its tendon transversely from the spine of the ilium, towards the lower third of the rectus, about an inch above the external ring, thus preserving Poupart's ligament arid the external ring for further examination, in relation to the anatomy of hernia. When the external oblique is raised, we see the inferior ribs, the inferior intercostal muscles, the internal oblique, and the cremaster. OBLIQUUS INTERNUS, or ASCENDENS, is also situated at the anterior and lateral part of the abdomen, broader before than behind, and more fleshy below than above ; it arises tendinous, but soon becomes fleshy, from the fascia lumbo- rum, from all the crest of the ilium, and from the two ex- ternal thirds of the grooved or abdominal surface of Pou- part's ligament, the fibres diverge in a radiated manner ; those from the lumbar fascia and posterior part of the ilium ascend obliquely forwards ; those from the anterior part of the ilium pass transversely, and those from Pou- part's ligament descend obliquely inwards ; the fibres con- tinue fleshy further forward than those of the external ob- lique ; at the linea semilunaris they end in a flat tendon, which, at the edge of the rectus, divides into two layers, to enclose this muscle ; the anterior is united to the tendon of the external oblique, the posterior and thinner layer is joined to the tendon of the transversalis ; about midway between the umbilicus and the pubis, the tendon of the in- ternal oblique does not divide, but the whole passes in front of the rectus, along with the tendon of the transversa- lis, to which it is closely connected; a little above the pu- bis these two tendons are inseparably joined, and are call- ed the conjoined tendons. The internal oblique is inserted, tendinous and fleshy, into the cartilages of the six inferior ribs, tendinous into the ensiform cartilage, and into the whole length of the linea alba ; the conjoined tendons are inserted into the symphisis and upper edge of the pubis, and passing external to the rectus are also inserted into the linea innominata, where they are connected with Gim- bernaut's ligament, and inseparably joined to the fascia transversalis ; these conjoined tendons lie posterior to the spermatic cord and to the triangular ligament, and afford much security to that part of the abdomen behind the ex- 144 DUBLIN DISSECTOR. ternal abdominal ring. Use of the internal oblique mus- cle, to assist the external oblique in expiration, and in com- pressing the abdominal viscera, also in bending the trunk forwards, or to one side ; it can also rotate the trunk, but in doing so, it co-operates with the external oblique of the opposite side, with which it forms a sort of digastric mus- cle ; this muscle is covered by the external oblique and latissimus dorsi; it lies on the transversalis muscle ; some small vessels ramify between them : a, small portion of the internal oblique is sometimes superficial, between the ex- ternal oblique and latissimus dorsi, and above the posterior part of the ilium. [Variety. This muscle also, is sometimes deficient at some parts.] Along the inferior border of this muscle we observe the following : CREMASTER, consists of a fasciculus of pale fleshy fibres, which arise from the internal surface of the external third of Poupart's ligament, and from the lower edge of the last described muscle ; a few fibres also sometimes proceed from the lower edge of the transversalis muscle ; it fre- quently too has a tendinous attachment to the pubis, be- hind the external abdominal ring ; the fibres all pass down- wards and forwards around the spermatic cord, but chiefly along its outer side, many of them in the form of arches reversed or concave upwards ; they are inserted into the tunica vaginalis ; a few fibres are lost in the scrotum. Use, to support, compress, and raise the testicle and its vessels ; the origin of this muscle is covered by the tendon of the external oblique, and lies on the fascia transversalis ; a small but long nerve, a branch from one of the lumbar nerves, runs between its fibres ; the lower part of the mus- cle is superficial and very pale ; in cases of old hernia, the fibres of the cremaster are found greatly increased in thickness and are often of a yellow colour ; and in that form of the disease called the oblique, or common inguinal hernia this muscle always forms one of the coverings of the sac. The cremaster is absent in the female. This muscle is probably formed incidentally, the testis, in its descent to the scrotum, carrying before it the lower bor- der of the internal oblique ; hence too the arched direction of some of its fasciculi. Raise off the internal oblique from the transversalis muscle ; commence above the ante- rior part of the crest of the ilium, where the muscles are separated by cellular membrane, and some branches of the circumflex-ilii vessels, make one incision from the ilium towards the cartilage of the ninth rib, and another from the ilium, towards the lower third of the linea semilunaris ; DUBLIN DISSECTOR. 145 carefully dissect off the posterior part of the muscle, to- wards the spine, and the anterior towards the rectus ; this portion can be separated from the transversalis, a little be- yond the linea semilunaris. TRANSVERSALIS, somewhat square, broader anteriorly than posteriorly, arises tendinous from the fascia lumbo- rum and the posterior part of the crest of the ilium, fleshy from the remaining anterior part of the crest, and from the iliac third of Poupart's ligament ; it also arises tendinous from the two last ribs, and by fleshy slips from the inner side of the five succeeding ; these indigitate with the ori- gins of the diaphragm ; all the fibres pass transversely forwards, except the most inferior, which are curved a lit- tle downwards ; they all end in a flat tendon, which, near the linea semilunaris, joins the posterior lamina of the in- ternal oblique, and is inserted along with it into the whole length of the linea alba, into the upper edge of the pubis, and into the linea innominata ; this tendon passes behind the rectus superiorly ; but inferiorly, that is, about mid- way between the umbilicus and the pubis, the conjoined tendons pass anterior to this muscle, and are inserted in the manner before mentioned. The transversalis abdominis is covered by the internal and external oblique ; it lies on the fascia transversalis and on the peritonaeum. Use, to compress the abdominal viscera, and assist in expiration ; this muscle is tendinous before and behind, fleshy in the middle, also above and below, contrary to the two oblique muscles ; the posterior tendon is described by some, not improperly, as dividing into three layers, which are in fact the three sheets or leaves of the lumbar fascia ; the poste- rior, very strong, is continuous with the fascia lumborum ; the middle, thinner and weaker, is attached to the trans- verse processes of the lumbar vertebrae ; and is separated from the former by the lumbar muscles ; and the anterior lamina, which is the weakest, is expanded over the qua- dratus lumborum, and the inferior part of the diaphragm, and is connected to the sides of the bodies of the lumbar vertebrae. The inferior edge of the transversalis is in some degree confounded with that of the internal oblique ; parti- cularly at their origin from Poupart's ligament ; it seldom, however, descends as low as that muscle, and it crosses the spermatic cord, or round ligament, just as either of these is about to enter the abdomen : the conjoined ten- dons also often admit of separation inferiorly near the ex- ternal ring, when the tendon of the transversalis muscle may be traced very distinctly behind the cord, intimately united to the transversalis fascia. Replace the oblique muscles, divide their tendons all along the side of the linea 13 146 DUBLIN DISSECTOR. alba, and dissect them off the rectus towards the linea se- milunaris; this anterior part of the sheath adheres so closely to the linese transversse, that it is difficult to sepa- rate it from them. RECTUS, long and flat, broader above than below, arises by a flat tendon, which is sometimes double, from the up- per and anterior part of the pubis, ascends parallel to its fellow, becomes broad and thin above the umbilicus, and is inserted into the anterior part of the thorax by three fasciculi, the internal one of which is fixed to the ensiform cartilage and costo-xiphoid ligament ; the middle, longer, and thinner, to the cartilage of the sixth rib ; and the ex- ternal, still broader and thinner, to the cartilage of the fifth rib. Use, to bend the chest towards the pelvis, or to raise the latter towards the chest, also to compress the ab- domen. The rectus is covered superiorly by the great pectoral, in the middle by the tendon of the external, and the anterior layer of that of the internal oblique muscle, and inferiorly by the external oblique and the conjoined ten- dons of the internal oblique and transVersalis, also by the pyramidalis. These muscles are much nearer to each other below than above ; they are each enclosed in a dis- tinct sheath, which consists, anteriorly, of the tendon of the external oblique and the anterior lamina of the inter- nal oblique, posteriorly of the posterior layer of the inter- nal oblique, and the tendon of the trans versalis. This sheath commences at the edge of the thorax, and terminates midway between the umbilicus and the pubis ; below which, all the tendons pass anterior to this muscle. If this part of the rectus be divided, the deficiency in the back of the sheath will be obvious, as it generally terminates ab- ruptly by a lunated edge ; in some cases, however, it ends gradually : the epigastric vessels ascend within this sheath, on the posterior surface of the muscle. The sheath of the rectus serves to confine this muscle in its proper place, and t'o prevent it, when contracted, from injuring the abdomi- nal viscera immediately behind it ; it also strengthens the parietes of the abdomen, and prevents the more frequent occurrence of hernia ; the deficiency in the back part of the sheath below, may permit the abdominal muscles to exert more direct influence on the urinary bladder when distended. The rectus is intersected by three or four irregu- lar, or zigzag, transverse, tendinous lines ; one of these is always to be found opposite the umbilicus, a second mid- way between this and the xiphoid cartilage, opposite to which a third is always placed ; if a fourth exist, it will be found below the umbilicus : these intersections are not com- plete ; they are generally deficient on the back part of the DUBLIN DISISSECTOR. 147 muscle ; the anterior part of the sheath adheres intimately to each of them, some fleshy fibres pass over one line and are inserted into those above and below, hence the .poste- rior fasciculi are longer than the anterior; by means of these lines the rectus is a sort of polygastric muscle, and is enabled to act in distinct or separate portions, so as to compress different parts of the abdomen in succes- sion, each section having a distinct nerve. [Varieties. This muscle is attached to the eighth rib, when that bone reaches the sternum, as is sometimes the case ; it also some, times ascends as high as the fourth rib, in other cases as high as the neck, in front of the pectoralis major.] Anterior to the origin of the rectus is the following small muscle : PYRAMIDALIS, is sometimes absent, it arises broad and fleshy from the pubis, ascends obliquely inwards, and is inserted narrow and tendinous into the linea alba, midway between the umbilicus and pubis. Use, it assists the rec- tus, and makes tense the linea alba ; it is covered by the tendon of the external oblique, by the triangular liga- ment and the conjoined tendons : it appears in some cases to be enclosed in a splitting of the latter. [Varieties. This muscle is often wanting, sometimes there are two, three, and even four on a side.] Dissect off the transversalis muscle in a direction from the ilium towards the linea semilunaris, and the fascia transversalis will be exposed covering the peritonaeum ; this fascia is connected to the internal lip of the ilium and to the whole length of Pou part's ligament, as far as the third insertion or Gimbernaut's ligament, from which it is con- tinued behind the rectus to that of the opposite side ; from these attachments, the fascia transversalis ascends between the peritonaeum and the transversalis muscle, as high as the diaphragm, and as far back as the psoas magnus ; it is very strong and tense inferiorly for about an inch above Poupart's ligament, but superiorly it is little more than condensed cellular membrane : this fascia serves to sup- port the peritonaeum, particularly at the inferior part of the abdomen, where the internal oblique and transversalis muscles are deficient ; the spermatic cord or the round ligament always perforates this fascia about three quarters of an inch above Poupart's ligament, and about an inch and a half from the tuberosity of the pubis ; this perfora- tion is called the internal abdominal ring, and is situated about midway between the spine of the ilium and the symphisis pubis; it is not a distinct opening, for the edges are prolonged along the cord, and lost in its cellular cover- 148 DUBLIN DISSECTOR. ing. The interval between the internal and external ab- dominal rings is traversed by the spermatic cord, and is named the inguinal or spermatic canal, to the anatomy of which the student should particularly attend, as the disease of inguinal hernia is situated here, in the treatment of which a correct knowledge of this region will be required. The spermatic or inguinal canal commences at the internal ring, and leads obliquely downwards, forwards, and inwards to the external ring, where it terminates ; this passage is bounded anteriorly by the skin and fascice, the tendon of the external oblique, and by the inferior fleshy margin of the internal oblique and transverse muscles, posteriorly by the transversalis fascia and by the conjoined tendons of the two last named muscles, inferiorly by Pou part's li- gament and its third insertion, superiorly this space is closed by the apposition of its opposite sides ; in the male the spermatic cord and cremaster muscle, and in the female the round ligament of the womb passes through this canal, the obliquity or valve-like structure of which serves to protect the abdomen against a protrusion of its contents. Inguinal hernia occurs more frequently in the male than in the female sex, in consequence of the spermatic cord and the inguinal rings in man being larger than the liga- mentum teres or these openings in the female : there are two species of this disease, oblique and direct. Oblique inguinal hernia is the more common form ; in this case, the peritonaeum or hernial sac, with its contents, protrude through the internal ring along the anterior part of the spermatic vessels, carrying before it the surrounding cel- lular tissue and a prolongation of the fascia transversalis from the edges of the opening ; this covering of the her- nial sac is called the fascia propria of inguinal hernia, and by some the fascia infundibuliforme. When the tumour has arrived at the lower edge of the transversalis and inter- nal oblique it insinuates itself between the cremaster mus- cle and the vessels of the cord, along which it descends to the external ring, where it is in general delayed for some time ; the form of this opening and the inter-columnar fas- cia preventing its free passage through it; as the sac, however, descends towards the scrotum these inter-colum- nar fibres become closely united to the cremaster, and are gradually elongated on the surface of the tumour. If the sac of an oblique inguinal hernia which has passed the external ring be carefully dissected, it will be found covered by the following parts ; beneath the integuments the superficial fascia, in general much thickened and divisi- ble into several laminae, will be seen to surround the tumour ; on dissecting off this, the fibres of the cremaster, in general DUBLIN DISSECTOR. ] 49 also thickened, will be observed spread on the forepart and sides of the sac, the inter-columnar bands from the external oblique tendon will be found closely connected to this mus- cle, and both will form a sort of capsule for the sac, sus- pending it towards the abdomen ; if this covering be divided, the fascia propria will appear closely investing the tumour, and so adhering to it as to be separated with difficulty from it ; this covering can often be divided into several layers, it presents, however, great difference in different cases; be- neath this, the hernial sac or the peritoneum will be found, which also in cases of old hernia will be considerably thick- ened ; on opening the hernial sac, its contents, either omen- turn or intestine, will be seen. The student should next at- tend to the situation of the epigastric vessels and their rela- tion to the parts concerned in oblique inguinal hernia ; these vessels are placed behind the fascia transversalis between it and the peritoneum, and in general can be discerned through the fascia ; if not, a little dissection will render them appa- rent ; two veins usually accompany the artery, one on either side ; sometimes there is but one epigastric vein, and that is on the pubal or inner side of the artery ; the epigastric artery arises from the external iliac near Poupart's ligament ; it first descends a little forwards and inwards, then ascends toward the rectus muscle, immediately behind the fascia transversalis, and very near to the inner or pubal side of the internal abdominal ring ; in oblique inguinal hernia the neck of the sac is nearly in contact with the epigastric vessels, which thus bound it on its internal side, hence the rule of practice, in performing the operation for the relief of stran- gulated oblique inguinal hernia, when the stricture is seated in the neck of the sac, is, to direct the edge of the knife or bistoury upwards and outwards. Direct or ventro-inguinal hernia protrudes directly through the external ring without descending along the spermatic channel : the occurrence of this disease is in a great degree guarded against by the fascia transversalis, and by the conjoined tendons which lie imme- diately behind the external ring : the edge of the rectus> the triangular ligament, and the spermatic cord may be also all enumerated as additional protections to this part of the abdo- men : in this species of hernia the sac will be found covered only by the integuments, superficial fascia, and some ten- dinous and aponeurotic bands it may have carried before it ; it is not covered by the cremaster, and in general it descends along the inner and anterior side of the cord, that is, the cord will be found external and inferior or posterior to it, but in some few cases the cord has been found passing across the neck of the sac, that is, anterior to it ; the sac is never, however, found between the cremaster muscle and 13* 150 DUBLIN DISSECTOR. the spermatic vessels. The epigastric vessels lie to the iliac or outer side of the neck of the sac ; in dividing the latter, therefore, in case this operation be required during life, the edge of the knife should be directed upwards and inwards. When the disease of oblique inguinal hernia has continued for a considerable length of time, the spermatic canal will be found altered in many respects from its natural condi- tion; it will have become dilated and shortened, and the abdominal rings expanded and approximated so as to render it difficult to distinguish the oblique from the direct inguinal hernia. This is the condition of the inguinal canal in the infant ; on account of the narrow pelvis, the canal is then short, the rings are more nearly opposed, and of course, if the same exciting causes were present, hernia would be more frequent in its occurrence. In connexion with inguinal hernia, the student may next study the anatomy of the groin in reference to crural hernia, or he may postpone this dissection until the contents of the abdomen have been examined and removed ; we shall, how- ever, here subjoin the description of the parts concerned in this disease : remove the integuments from the anterior part of the upper third of the thigh, the superficial fascia will be seen descending over Poupart's ligament to invest the lower extremity ; in the groin this fascia is very thick, and may be divided into several layers, which are separated by lym- phatic ganglia and the superficial inguinal vessels; this fascia may be easily raised from the fascia lata on the outer and inner sides of the thigh, but in the middle of the groin and about an inch below Poupart's ligament, these fasciae are almost inseparably joined ; when the superficial fascia shall have been dissected off the forepart of the thigh, we shall see several lymphatic ganglia, the saphena vein and some small blood vessels lying on the fascia. The form and boundaries of the inguinal region also may then be more distinctly seen ; the term crural is some- times applied to this space, and that of inguinal to the smaller region above Poupart's ligament ; I prefer naming the latter spermatic, and the former inguinal or superior crural. The inguinal region is triangular, the base is Poupart's ligament ; the apex is, inferiorly, formed by the meeting of the sartorius and adductor muscles, at the lower part of the upper third of the thigh ; the external side is very prominent, and con- sists of the sartorius, iliacus, rectus and other muscles, all covered by the fascia lata ; the internal or pubic side is flat and on a plane posterior to the iliac ; it is formed by the pectinseus and adductor muscles, also covered by the fascia lata. The inguinal lymphatic ganglia are irregular in num- DUBLIN DISSECTOR. 15 ber, and size, they are in general about twelve in number, and may be divided into a superficial and a deep set ; the former are the more numerous, and may be arranged from their situation into the superior and inferior ; the superior are small, four or five in number, lie parallel to Poupart's ligament, some above, others below it ; the inferior are two or three in number, larger than the former, and placed perpendicularly or parallel to the saphena vein ; in general one lies behind this vessel ; the deep inguinal ganglia are be- neath the fascia lata, are three or four in number, and are closely connected to the sheath of the femoral vessels, chiefly to its inner side ; in general one occupies the femoral ring. The saphena vein is the principal cutaneous vein of the lower extremity ; it will be seen in a future dissection to arise from the dorsum and inner side of the foot, and to ascend in front of the inner ankle along the inner side of the leg, and pass- ing behind the inner condyle of the femur it continues to ascend along the inner and anterior part of the thigh to within about an inch and a half or two inches of Poupart's ligament, when it begins to pass through an opening in the fascia lata, (the saphenic opening,) it then joins the femoral vein about an inch or an inch and a half below the crural arch. The saphenic opening in the fascia lata will be very distinctly seen if the vein be divided on the thigh and raised towards Poupart's ligament, it presents a well-marked semi- lunar edge, the concavity looking upwards ; the edge, though apparently sharp, yet if carefully examined will be found reflected backwards on the shea'th of the femoral vessels ; remove the inguinal ganglia, clean the surface of the fascia lata, to the connexions of which in this region the student should next attend. The fascia lata may be observed to be united to the spine of the ilium, to the whole length of Pou- part's ligament, also to the linea innominata and spine of the pubis ; it covers the muscles on either side of the groin, and the vessels in the middle ; for the purpose of more par- ticular examination, this fascia may be divided into three portions, the internal or pubic or pectineal portion, the ex- ternal or iliac, and the middle or cribriform ; the internal or pubic portion covers the pectinseus, gracilis, and adductor muscles, and is inserted internally into the ramus of the ischium and pubis ; superiorly into the linea innominata or ilio-pectinea, anterior to Gimbernaut's ligament ; externally it passes behind the sheath of the femoral vessels, and at the edge of the psoas tendon divides into two lamince, one passes beneath that tendon, and is attached to the capsular ligament of the hip-joint ; the other passes over that tendon and is continued into the deep surface of the fascia iliaca. The middle portion of the fascia lata is very thin, and has been 152 DUBLIN DISSECTOR. termed the cribriform fascia ; this extends from the saphena vein to Poupart's ligament, and is connected on either side to the pubic and iliac portions of the fascia lata. The cri- briform fascia covers the femoral vessels, and is perforated by the lymphatic vessels passing to the iliac ganglia ; this portion of the fascia lata is more closely connected than any other to the superficial fascia : indeed in structure it resem- bles the superficial more than the fascia lata, nor are its fibres directly continued from those of the fascia lata ; some have, therefore, considered the cribriform fascia as a deep lamina of the superficial fascia ; in many cases, however, it has an aponeurotic structure, and appears to be clearly derived from the iliac portion, and inserted into the pubic portion of the fascia lata ; it presents much variety in this respect. The external or iliac portion of the fascia lata is very dense and strong, it is continued from the external sur- face of the thigh, and is intimately attached superiorly to the spine of the ilium, and to Poupart's ligament ; and uniting with the cribriform fascia, is continued in front of the femoral vessels, along with the inferior fibres of Pou- part's ligament, and is inserted along with these into the linea innominata, thus assisting to form the external part or the base of Gimbernaut's ligament. If the cribriform fascia be removed along with the superficial fascia, then the iliac portion of the fascia lata will present the appearance of a crescentic or falciform process, extending across the femoral vessels, the concavity of which process will look downwards and inwards : the inferior cornu joins the external cornu of the saphenic opening, and the superior cornu is inserted along with the posterior fibres of Poupart's ligament, or Gimbernaut's ligament, into the linea innominata, on the internal border of the crural ring ; although this crescentic process appears to present a defined edge, yet if the latter be examined closely it will be found reflected backwards on the sheath of the vessels and on the muscles, in the same manner as the apparent edge at the lower part of the saphe- nic opening. Next direct your attention to the internal surface of the crural arch, and to the connexion between it and the deep fasciaB of the abdomen, viz. the transversalis and iliaca ; divide the fascia transversalis from the spine of the ilium towards the rectus muscle ; dissect it carefully down from the peritonaeum, then push up this membrane, together with the caecum or sigmoid flexure of the colon, out of the iliac fossa, to which they are connected by very loose cel- lular membrane ; we thus obtain a view of the internal surface of Poupart's ligament, and of the parts which pass beneath it, and which naturally fill the space or cavity of DUBLIN DISSECTOR. 153 the crural arch : first, observe the fascia transversalis at- tached to the inner lip of the ilium and to Poupart's liga- ment from the spine of that bone, as far as the pubis, into the linea innominata of which it is inserted ; here also it is inseparably joined to the conjoined tendons of the inter- nal oblique and transverse muscles ; as this fascia is pass- ing anterior to the iliac or femoral vessels, a portion of it extends beneath Poupart's ligament, in front of these ves- sels, so as to form the anterior part of their sheath ; this pro- cess of the fascia transversalis soon becomes thin and in- distinct, and is lost in the cribriform part of the fascia lata. The fascia iliaca is a tolerably strong aponeurosis ; it co- vers the iliac and psoas muscles, passes behind the iliac vessels, and adheres to the upper margin of the pelvis ; ex- ternally it is connected to the inner edge of the ilium, and inferiorly it is attached to Poupart's ligament, and to the fascia transversalis, from the spine of the ilium as far in- wards as the iliac artery ; here it presents a semilunar edge, separates from Poupart's ligament, and from the fas- cia transversalis, passes behind the femoral vessels, forms the posterior part of the sheath, adheres to the pubis, and to the capsule of the hip joint, and is connected to and conti- nuous with the pubic or pectinseal portion of the fascia lata. The fasciae transversalis and iliaca may be com- pared to a funnel, containing in the superior wide portion the peritonaeum and its contents, and enclosing in the in- ferior narrow part, or pipe, the femoral vessels, and one or two lymphatic ganglia ; of this funnel the fascia transver- salis forms the anterior, and the fascia iliaca the posterior wall ; these fasciae may now be seen to be perfectly conti- nuous with each other, between the vessels and the spine of the ilium, different names only being applied to differ- ant portions of one extensive aponeurosis ; as the iliac and transverse fasciae are continued one into the other, exter- nal to the iliac artery, a white line may be observed ; this is the circumflex ilii artery enclosed in a sort of canal be- tween these fascice and Poupart's ligament, to which these aponeuroses are united. The student should next consider how the space, com- monly called the crural arch, is naturally filled ; that por- tion of it between the spine of the ilium and the iliac or femoral artery is occupied by the psoas and iliac muscles ; imbedded between these muscles is the anterior crural nerve ; on the pubic side of these muscles is the femoral artery, next to which is the femoral vein, and at a little distance to the pubal side of this vessel is Gimbernaut's ligament, which closes the internal part of this space ; thus, almost all the crural arch is filled, except a small portion 154 DUBLIN DISSECTOR. between the femoral vein and the third insertion of Pou- part's ligament; this space is the femoral or crural ring; this is somewhat of a triangular form, the base, externally, is the femoral vein, the apex internally is Gimbernaut's ligament ; it is bounded anteriorly by Poupart's ligament, and by the superior fibres or cornu of the falciform pro- cess of the fascia lata, and posteriorly by the pubis, cover- ed by the pectinseal muscle, and by the pectina3al portion of the fascia lata ; the spermatic cord or the ligamenturn teres lies on the anterior boundary of this opening, Gim- bernaut's ligament prevents femoral hernia occurring in- ternal to this space, which is the only part in the crural arch where a hernia can descend, and even here this acci- dent is in a great degree guarded against, as a lymphatic ganglia generally occupies this situation, and a layer of condensed cellular membrane extends across the opening ; this must be carried down before the hernial sac, so as to form a covering for it, and hence it has been named the fascia propria; this fascia, though often weak and indis- tinct in the natural and healthy state, becomes very thick and strong in cases of old femoral hernia : the fascia pro- pria may be described as arising thin and delicate from the fascia iliaca on the external side of the iliac vessels ; passing over these vessels it descends internally into the pelvis; inferiorly it is continued along these vessels to Poupart's ligament, covers the femoral ring, and then as- cending' is lost on the inner surface of the fascia transver- salis. Crural hernia cannot occur external to the ring, as there the femoral vessels fill up the space, and strong partitions pass from the fascia transversalis to the fascia iliaca on the inner side of the vein, and between it and the artery ; these septa prevent the distention of the sheath ; the fascia propria also rounds off the angle betw r een the fascia transversalis and the forepart of the vessels, and prevents a hernia occurring in front of the artery or vein ; external to these vessels the crural arch is completely closed by the close connexion between the fasciaa trans- versalis and iliaca and Poupart's ligament, in front of the psoas and iliac muscles. Femoral hernia then can occur only at the femoral or crural ring ; this disease is more frequent in the female than in the male, the crural arch and ring being larger in the former than in the latter; femoral hernia descends through a sort of canal which commences at the crural ring, and ends at the saphenic opening in the fascia lata, through which the sac pro- trudes ; the hernial sac in descending carries before it the fascia propria, descends in the sheath of the vessels along the inner side of the vein, and may remain in this situa- DUBLIN DISSECTOR. 155 tion for a considerable time ; as the tumour increases in size it bursts through the sheath, and either tears or dilates some opening in the cribriform fascia, and then turns for- wards into the groin ; if the tumour increase still further, it is found to turn upwards over Poupart's ligament, and to rest on the lower part of the tendon of the external oblique ; the form of the crural ring, the course of the superficial epigas- tric vessels, and the close connexionfl&etween the superficial and cribriform fasciae account for its ascending in this manner. If we dissect off the integuments from a femoral hernia of long standing, we shall find beneath them the superficial fascia so increased in thickness and vase ularity as to present, a compact and almost fleshy-like appearance ; when this shall have been divided, the tumour can be brought down off the abdomen into the groin, and will be found covered by a dense and smooth capsule, which often presents a glossy appearance ; this is the fascia propria ; in dissecting off this, it will in general be found to consist of several laminae, which sometimes separate so easily and appear so distinct as to lead an inexperienced operator to suppose that the hernial sac itself is exposed. These then are the coverings of the sac, which is thus placed external or superficial to the fascia lata : the neck of the sac, how- ever, it is to be recollected, lies deep within the sheath of the vessels, and is, therefore, covered by the fascia trans- versalis, and by the superior cornu of the falciform pro- cess of the fascia lata. Let the student now review the dissection that has been made ; let him move the thigh in different directions, and he will remark that, when it is ro- tated inwards, Poupart's and Gimbernaut's ligaments, as well as the fascia lata feel relaxed, and that the crural ring will feel larger or more dilatable ; let him also ob- serve the relation of the femoral vein, the epigastric ves- sels and the spermatic cord or round ligament to this open- ing ; pass up the finger from the groin into the crural ring, and suppose that the stricture on femoral hernia was seat- ed here, and that this opening required to be dilated, he will now perceive that this may be done with most safety by directing the edge of the bistoury forwards and a little inwards, so as to divide the external edge or base of Gim- bernaut's ligament, which edge is composed of the inser- tion of the superior cornu of the falciform process of the fascia lata ; the stricture on femoral hernia may, however, be seated lower down than'in the neck of the sac ; it may be situated in that opening of the cribriform fascia through which the hernial sac has protruded ; in such a case, the stricture may be divided by directing the edge of the knife directly inwards along the surface of the pectinseus muscle 156 DUBLIN DISSECTOR. The following measurements of the parts engaged in, or referred to in the foregoing account of the anatomy of the inguinal and femoral hernisehave been extracted from Cooper's valuable work on Hernia, and have been sanc- tioned by several other writers on the same subject : I have tested these very frequently, and though I can bear testi- mony to their general accuracy, I must observe, I have found deviations to have occurred so frequently, and in cases where there was no a priori reason to expect such, that I do not consider these numbers as facts of much value, or of any material practical importance. Male. Female. From the symp. pubis to the ant. sup. spinous process of the ilium, 5i| in. 6 in. to the tuberosity of pubis, - - 1 1| to the inner margin of ext. ab- abdominal ring, - - - - OJ 1 to the inner edge of internal abdnm. ring, ------3 3 to the middle of iliac artery, 3 3$ to the middle of iliac vein, - 2| 2$ to the origin of epigastric ar- tery, -------- 3 3^ to the epig. art. on the inner edge of ext. abdoin. ring, - 2$ 2 to the middle of lunated edge of fascia lata, ----- 3^ $ to the middle of crural ring, - 2j 2| From ant. edge of crural arch to saphona major vein, ----- i j| From symp. pubis to centre of oririce of femoral hernia! sac, - - 2 2j From centre of orilice of do. to external iliac artery, ----- i j| to centre of ext. iliac vein, - 0$ to origin of epigastric artery, ----- oif 1 to inner edge of int. ab- dominal ring, - - - 1 ij. From tuberosity of pubis to centre of orifice of fern, hernial .sac, . 1 l (.Inat. and Surg. Treatment of Jbdom. Hernia^ by Sir A. COOPER. Bart. 2nd edit, by C. A. Keys.) SECTION II. DISSECTION OF THE VISCERA OF THE ABDOMEN. THE abdomen is the largest cavity in the body ; it is of an oval form ; its capacity, and in some degree its figure, differ at different ages and'in different subjects ; it is bound- ed superiorly by the diaphragm, anteriorly and laterally by the abdominal muscles, inferiorly by the true and false pelvis, and posteriorly by the lumbar vertebrae, the crura of the diaphragm, and the psoae and quadrati lumborum muscles. Although the expression "cavity of the abdo- DUBLIN DISSECTOR. 157 men" is in common use, it is not correct, for during life there is no cavity, as the diaphragm and abdominal muscles by their alternate action keep up such a constant and uni- form pressure on the viscera, that these and the parietes are always in perfect contact. The abdomen contains the per- itonaeum and the organs of digestion ; the kidneys, renal capsules and ureters; also the thoracic duct, the sympa- thetic nerves, the aorta, vena cava, and the numerous branches of these vessels. The abdomen is generally di- vided by writers into nine, but by some into twelve re- gions ; by drawing two transverse lines, one between the extremities of the cartilages of the ninth ribs, and the other between the anterior superior spinous processes of the ossa ilii, we may define three regions ; the epigastric above, the umbilical in the middle, and the hypogastric below ; and then by drawing a vertical line on each side from the ex- tremity of the ninth rib to the anterior superior spinous process of the ilium, we shall subdivide each of these re- gions into three parts : the three divisions of the epigastric region are the epigastrium, or scrobiculus cordis in the cen- tre, and the right and left hypochondriac regions on either side: the epigastrium is immediately below the ensiform cartilage, and the hypochondriac regions are covered by the false ribs ; the lateral portions of the umbilical division are the lumbar regions ; the middle of the hypogastric re- gion is the hypogastrium, and the lateral portions are the iliac regions ; the lower part of the hypogastrium is called by some the pubic region, and the lower part of each iliac division is called inguinal region, or more properly spermatic, (the term inguinal being commonly applied to the upper and anterior part of the thigh,) and contains the iliac ves- sels, and in the male the spermatic cord, and in the female the round ligament of the uterus. The viscera, which constantly or occasionally occupy the regions of the abdomen will be seen when the peri- tonseal cavity has been opened, and with these the student should make himself familiar, as this knowledge may be of practical importance in cases of wounds penetrating this cavity, or in making an examination during life to detect any suspected organic disease. Dissect the abdominal muscles off' the peritonaeum; these can be easily separated laterally and inferiorly; but anterior- ly, particularly near the umbilicus, it will be found very difficult to detach the sheath of the rectus from this membrane. The external surface of the peritoneum, which is thus exposed, appears rough and cellular, from its connexion to the superincumbent muscles ; three ligamen- tous cords are seen extending along it anteriorly and infe- 14 158 DUBLIN DISSECTOR. riorly, from the summit and sides of the urinary bladder towards the umbilicus ; the central one of these is the re- mains of the urachus, and that on each side is the obliter- ated umbilical or hypogastric artery ; anteriorly and su- periorly we perceive another ligamentous substance, as- cending from the umbilicus obliquely backwards, and to the right side ; this is the remains of the umbilical vein ; it is at first placed between the peritonaeum and the mus- cles, but it soon sinks deep towards the liver, carrying around it a fold of peritonaeum, named the suspensory liga- ment of the liver, which will be seen when the peritonaeum is opened ; the epigastric vessels also may be observed as- cending from each inguinal region, and branches of the internal mammary arteries descending on the surface of this membrane. Next open the peritonaeum by an incision from the ensiform cartilage to the umbilicus, and from this point carry another on each side obliquely downwards, to the spine of the ilium : on throwing down the inferior flap thus formed, we remark on its internal surface the projec- tions of the three ligamentous cords which were before noticed as ascending from the bladder to the umbilicus ; we may also remark how the external of these cords, or the obliterated umbilical artery on each side, throws the lower part of the peritonaeum into pouches, two on each side, the external and internal inguinal pouches or fosscc ; the former lies between the ilium and the obliterated hypogas- tric vessels, the latter between this cord and the fundus of the bladder. The external pouch is large and very con- cave internally, and appears to protrude towards the in- guinal canal : the existence of this pouch may conduce to the production of oblique inguinal as well as of femoral hernia : the internal pouch lies behind the external ring, and becomes protruded in direct or ventro-inguinai hernia. When the peritonaeum has been fully opened, we perceive its inner surface smooth and polished like all serous mem- branes, and filling its cavity we see the numerous digestive organs ; these, though apparently within this bag, are real- ly behind it, and only protrude the posterior side of this large sac into the cavity ; nothing is contained within the peritonseum but the serous fluid, which is constantly exhaled, for the purpose of lubricating its opposite sides. We also obtain a partial view of the following organs., which in general occupy the same situation during life as we per- ceive them now to hold. Filling the right hypochondrium is the liver, with the fundus of the gall bladder projecting a little below it. In the epigastric region we see a portion of the liver also, resting on the stomach, and below it we see the pylorus and the commencement of the duodenum ; DUBLIN DISSECTOR. 159 in the left hyponchondrium lie the spleen and great ex- tremity of the stomach ; in the right and left lumbar re- gions we find the colon, ascending through the former, and descending through the latter, behind which is each kidney ; the duodenum also partly occupies the right lumbar region ; through the proper umbilical region the transverse colon runs, not fixed, however, in any particular part of it, and from this intestine we perceive the great omentum descend- ing towards the lower part of the abdomen, presenting, however, very different appearances in different subjects : in some being expanded over the small intestines, so as nearly to conceal them ; in others being coiled up into a narrow fold, and often concealed in some recess between the surrounding viscera : the convolutions of the jejunum and ileum intestines occupy the lower part of the umbilical, and extend indifferently into the hypogastric, and iliac re- gions ; the csecum or caput coli is fixed in the right, and the sigmoid flexure of the colon in the left iliac fossa ; the rectum and other pelvic viscera occupy the hypogastric regions, but will of course change their own situation as well as that of the small intestines, according as they are contracted or distended. The student may next examine the anatomy of the peritonaeum; this is the largest serous sac or membrane in the body ; it lines the abdominal mus- cles, and covers almost all the abdominal viscera ; that portion which adheres to the parietes is called the parietal, and that covering the viscera the visceral layer. The peri- tonaeum is a shut sac, and therefore, when opened presents one continued surface, which may be traced throughout the whole extent without any interruption ; it covers the viscera in such a manner that they lie external or pos-. terior to it ; the familiar example of the double night-cap on the head has been, not unaptly, adduced, to explain how the viscera may be covered by the peritonaeum, and yet really lie beneath it or behind it. Let us now trace this membrane through its entire extent, commencing at the umbilicus ; from the transverse incision that was made into it in this situation, we may perceive it to ascend on the in- ternal surface of the transverse and recti muscles, as high as the margin of the thorax ; then bending back, it adheres to the inferior surface of the diaphragm, and continues very far back on this muscle, particularly in the left hy- pochondrium ; from the diaphragm it is reflected on the spleen on the left side, on the stomach in the centre, and on the liver on the right side ; it is also reflected on this last named viscus by a distinct fold, the falciform or suspenso- ry ligament, from the umbilicus, and from the abdominal muscles on the right side of the linea alba ; as the perito- 160 DUBLIN DISSECTOR. nseum is reflected from the diaphragm on each side of these organs in the epigastric and hypochondriac regions, it forms folds, which to a certain extent serve as ligaments ; these will be noticed more particularly in the examination of the individual viscera. Having covered the organs in the upper division of the abdomen, it is continued downwards in the following man- ner : having invested both surfaces of the liver as far as its transverse fissure ; it is conducted along and around the vessels of this gland towards the lesser curvature of the stomach ; this fold, which thus surrounds the hepatic ves- sels, is called the lesser or the gastro-hepatic omentum ; it is also sometimes named the capsule of Glisson ; at the lesser arch of the stomach the two laminae of this process separate to enclose the stomach, the posterior layer giving a serous covering to the back part of this organ, and in like manner the anterior layer covering its anterior sur- face, on which it is continuous with that portion of perito- naeum \vhich has descended from the diaphragm, and with that which is also continued from the spleen to the sto- mach. The peritonsenm having thus enclosed the stomach and its vessels between the two layers of the lesser omen- tum, we next observe that these laminae having passed the great curvature of the stomach touch each other, and being joined by the peritonaeum from the lower end of the spleen, descend under the name of the gastro-colic or the great omentum, to the lower part of the abdomen : in ge- neral it descends lower on the left side than on the right ; it then turns on itself, and ascends obliquely backwards to the arch of the colon, along the convex edge of which its laminae separate to enclose this intestine and its vessels ; along the concave edge of the colon these laminae again unite, and increasing in density form that process which is called the transverse meso-colon, which passes back- wards to the spine : opposite the duodenum this process separates into an ascending and descending layer ; the in- ferior division of the duodenum lies between these ; the ascending layer proceeds in front of the lower and middle divisions of the duodenum, up to the back part of the right lobe of the liver, where it becomes continuous with the peritonseal tunic of that viscus and with the posterior layer of the lesser omentum which is descending along the back part of the hepatic vessels. The descending layer of the transverse meso-colon expands into each lumbar region, in which it attaches the lumbar portions of the colon by a duplicature called the right and left lumbar meso-colon ; in the centre the inferior layer of the transverse meso-co- lon adheres to the vertebral column, and to the great ves- DUBLIN DISSECTOR. 161 sels which lie upon it, and is thence reflected forwards and downwards, over the small intestines and their vessels, and returns around these to the spine, thus forming a very important and remarkably folded or plaited process named the mesentery. From the inferior surface of the mesen. tery the peritonaeum extends into either iliac region, and descends into the pelvis in the middle ; it serves to connect the caecum in the right, and the sigmoid curve of the co- lon in the left iliac fossa ; in the pelvis the peritonaeum descends around the rectum, forming the process named the meso-rectum ; opposite the lower third of the sacrum, it is reflected to the lower and back part of the bladder, and in the female to the upper and back part of the vagi- na, from which it ascends on the uterus, and forms on each side of this organ the broad ligament which supports the Fallopian tube and the ovary ; the peritonaeum is then re- flected from the fore part of the uterus to the back of the bladder, ascends, both in the male and female, along the posterior surface and sides of this viscus to its superior fundus, from which, and from the iliac fossae, it is conti-. nued to the abdominal muscles ; forms the inguinal pouches, and may then be traced on the inner surface of the recti and transverse muscles up to the umbilicus, where the sac was opened. The different folds which the perjto, naeum forms in this course are termed processes, the prin- cipal of which, in addition to the ligaments of the several organs, which shall be noticed in the description of the latter, are the lesser omentum, the great omentum, the splenic omentum, the colic omentum, the appendices epi-. ploicae, the transverse, and the right and left lumbar meso- colons, the mesentery, meso-caecum and meso-rectum. The lesser or gastro-hepatic omentum consists of two lamU nse, which extend from the transverse fissure of the liver to the lesser curvature of the stomach and to the upper part of the duodenum ; it contains between its layers the vessels of the liver, viz. the hepatic artery to the left side, the ductus choledochus to the right, and the vena portse behind and between both ; at its connexion to the stomach, it encloses the coronary vessels of this organ ; the lesser omentum lies anterior to the foramen of Winslow ; this omentum seldom contains much fat. /The great or gastro-colic omentum also consists of two la- /minse, which descend from the lower end of the spleen, and from the anterior and posterior surface of the stomach ; between these laminae are several long and tortuous ves- sels, descending from the vessels of the stomach, and some adipose substance, the quantity of which varies very much in different subjects ; the great omentum descends in front 14* 162 DUBLIN DISSECTOR. of the large and small intestines to the lower part of the abdomen, in general lower on the left than on the right side ; (this explains the reason why the omentum is more frequently found in a hernial sac on the left than on the right side ;) it then turns upwards and backwards until it reaches the transverse arch of the colon ; that portion of omentum, therefore, which is inferior to the colon, consists of four laminae, two descending and two ascending ; these, in the young subject, can be separated from each other, and a distinct cavity can be seen between them ; this is part of the cavity or bag of the omentum which communi- cates with the general cavity of the peritonaeum by the opening of Winslow, and which will be more particularly described presently ; at the arch of the colon the two as- cending laminae of the great omentum separate to enclose this intestine, and again uniting, form the commencement of the following process. The transverse meso-colon extends from the concave bor- der of the arch of the colon backwards to the spine ; this process is very strong and dense, it encloses the vessels of the colon and forms a sort of division or partition in the abdomen between the epigastric and umbilical regions ; when the transverse meso.colon has arrived at the spine, its two laminae separate, one descends, the other ascends ; the descending layer is very strong, expands laterally into the right and left lumbar regions, in each of which it is reflect- ed either partially or perfectly around the ascending and descending colon, and thus forms a short fold or process very irregular in different subjects, termed the right and left lumbar meso-colons ; the inferior or descending layer of the transverse meso-colon is continued obliquely down- wards in the middle line to form the mesentery, a process which we shall trace when we have pursued the superior or ascending layer of the meso-colon to its termination. This lamina is thin and delicate ; it ascends in front of the inferior and middle portions of the duodenum, and of the pancreas ; it also covers the aorta and vena cava, and continues along this latter vessel to the liver, on the Spige- lian lobe of which it expands, and on it and on the right lobe, behind the foramen of Winslow, it becomes conti- nuous with the peritonaeum, which has been reflected on the back part of the liver from the diaphragm. As this ascending layer proceeds in front of the pancreas, it is continuous on each side with the posterior layer of the lesser omentum which covers the back part of the stomach. The ascending layer may be best seen and traced by di- viding the great omentum a little below the stomach, and raising this organ towards the thorax; we shall thus lay DUBLIN DISSECTOR. 163 open the cavity of the omentum, and shall be able to trace the parieties of this bag through their whole extent. The cavity of the omentum extends from the transverse fis- sure of the liver superiorly, to the lower border of the great omentum inferiorly ; it is bounded anteriorly by the lesser omentum, the stomach, and the anterior or descend- ing portion of the great omentum ; inferiorly it is formed by the great omentum turning on itself; and posteriorly it is bounded by the ascending portion of the great omentum, by the colon, by the transverse meso-colon, and by the su- perior or ascending layer of this process, which terminates at the liver. The cavity of the omentum communicates with the general peritonseal cavity through the foramen of Winslow ; this opening is situated in the lower part of the right hypochondriac region just above the right lumbar ; it is somewhat oval, bounded anteriorly by the lesser omentum and by the hepatic vessels, posteriorly by the termination of the ascending layer of the meso-colon which invests the vena cava, superiorly by the lobulus caudatus of the liver, and inferiorly by the superior portion of the duodenum ; if the membrane composing the omenta be perfect, and if air be forced through this opening, it will descend behind the stomach, and will inflate the omental cavity ; the great omentum, however, in general is so crib- riform that this experiment cannot be performed ; the prin- cipal use of this cavity is most probably to afford a ser- ous surface or cavity for the stomach to move or to distend into posteriorly during the progress of digestion. The splenic omentum extends from the fissure in the spleen to the great end of the stomach, and is continuous inferiorly with the great omentum ; the splenic vessels and the vasa brevia are contained between the laminae of this process. The colic omentum is a fold of peritonaeum which de- scends from the upper part of the right or ascending colon ; it generally lies posterior to the great omentum ; it is composed of two laminae, between which are contained blood-vessels and adipose substance. The appendices epiploica are attached all along the large intestine ; but principally to the transverse arch of the colon ; they are small prolongations of the peritonaeum, filled with a soft fatty substance ; they are never found at- tached to the small intestine ; they vary very much in dif- ferent subjects in number and size; their use is not as- certained. The mesentery is the largest and most remarkable process of the peritonaeum ; it is continuous with the descending layer of the meso-colon, and extends from the left side of 164 DUBLIN DISSECTOR. the second lumbar vertebra obliquely downwards to the right iliac fossa ; this is the root of the mesentery ; from this it expands very much, and is folded round the jejunum and ileum intestines, and then returns again to the spine or to the inferior surface of the root ; the laminee of the me- sentery can be easily separated ; between them we find the mesenteric arteries, veins and nerves, also numerous absor- bent vessels and ganglia ; the mesentery serves to support the convolutious of the small intestines and the numerous vessels passing to and from these. The meso-cacum is a fold of peritonaeum which attaches the caecum to the right iliac fossa ; this process, however, is frequently imperfect ; the posterior portion of this intes- tine being sometimes deprived of a serous coat, and con- nected to the iliac muscle by cellular membrane. The meso-rectum is a short fold of peritonaeum which con- nects the superior portion of the rectum to the upper and anterior part of the sacrum ; it encloses the hsemorrhoidal vessels and nerves. The viscera of the abdomen are the digestive and urina- ry organs ; the former we shall examine first ; they may be divided into the membranous and glandular. The membranous viscera are the stomach and intestinal tube ; the latter is divided into the small and large intestine ; the small intestine is subdivided into the duodenum, jejunum, and ileum ; the large intestine into the ca3cum, colon, and rectum. The glandular viscera are the liver, spleen, and pancreas. We shall consider the membranous viscera first, and commence with the description of the stomach, which is the most important part of the digestive apparatus, the principal change in the food being accomplished in this organ. The stomach is placed between the oesophagus and the duodenum, and communicates with both ; it is situated in the left hypochondriac and epigastric regions, and a small portion of it extends into the right hypochondrium ; from the left side it passes across the epigastric region, obliquely downwards and forwards, and near its right or pyloric ex- tremity it bends a little upwards and backwards. Tho stomach is connected to the diaphragm by the oesophagus and by the peritonaeum ; to the spleen by the splenic omen- turn ; to the liver by the lesser omentum, and to the arch of the colon by the great omentum. If the stomach be moderately distended with air or fluid, its form and con- nexions can be better understood; it will then appear somewhat of a conical figure, the base to the left side, the apex to the right, the intermediate part being somewhat curved ; it will present two extremities, the left and right ; DUBLIN DISSECTOR. 165 two orifices, the cardiac and pyloric [or cesophageal and duodenal ;] two surfaces, an anterior or superior, a poste- rior or inferior ; and two curvatures or edges, the lesser or concave, the greater or convex. The left or splenic extremity is very large, swells into the left hypochondrium beneath the ribs, so as nearly to conceal the spleen ; the right or pyloric extremity is much smaller, is cylindrical and slightly convoluted like an intestine ; it lies anterior and inferior to the left or splenic end, and extends to the fundus of the gall bladder or to the edge of the lobulus quadratus of the liver; it sometimes descends into the umbilical region. The cardiac orifice is the highest point of the stomach ; it is situated between the left or great end and the lesser cur- vature, about three inches distant from the former ; it is surrounded by vessels and nerves. The pyloric orifice is between the stomach and the duode- num ; it lies to the right side of the spine ; it is, in general, in contact with the liver and gall-bladder, and anterior to the pancreas ; it lies inferior, anterior, and to the right side of the cardiac orifice ; it has a peculiar firm, hard feel. The anterior surface looks upwards aud forwards, and is in contact with the diaphragm, the ribs and the left lobe of the liver. The posterior surface looks backwards and down- wards, and rests on the meso-colon. The lesser, or concave edge of the stomach, looks backwards and upwards to- wards the spine and lobulus Spigelii of the liver ; this edge, near the pylorus, is convex, the great edge being concave opposite to this ; the lesser omentum is attached to it, and the coronary vessels run along it. The great or convex edge looks forwards and downwards towards the colon; to it the great omentum and the epiploic vessels are attached : in the empty or contracted state of the stomach, these edges are thin and directed almost vertically, but when the stomach is distended, they become enlarged and round, and continuous with the surfaces. The stomach is composed of three tunics, a serous, a muscular, and a mucous ; these are connected to each other by two laminse of cellular membrane ; the serous or peri- ton&al coat is derived, as was before explained, from the la- minse of the lesser omentum, separating at the lesser cur- vature, expanding over its surfaces, and uniting along the convex edge, to form the great omentum : the serous coat is loosely united to the edges, but almost inseparably so to the middle of each surface and to the pyloric extremity ; a layer of very fine cellular tissue connects this to the fol- lowing tunic, the muscular ; this consists of fibres, which run in three different directions ; the first or superficial are longitudinal ; they are continued from the oesophagus, and 166 DUBLIN DISSECTOR. are very strong along the curvatures, particularly on the lesser ; the middle layer of fibres run circularly ; they commence at the left extremity, or cul de sac, and are ar- ranged in nearly parallel rings; they are very strong about the centre, where they often cause a constricted ap- pearance around the stomach, as if dividing it into two por- tions; the circular fibres again increase in thickness as they approach the pylorus : these fibres do not form per- fect circles ; the extremities of each fasciculus turn ob- liquely to one side ; the third set of fibres take a very irre- gular or oblique direction ; they are most distinct on the great end, or culde sac, and appear as a continuation of the circular fibres of the oesophagus. Beneath the muscular tunic is the second lamina of cellular tissue, which con- tains the minute divisions of the nerves and vessels of the stomach, and has been, by some, called the nervous coat of the stomach. The internal, or mucous or villous coat is very soft, and of a pale red or rose colour, sometimes in- terspersed with such very vascular patches as might lead the inexperienced to mistake them for the effects of inflam- mation : in order to examine this tunic of the stomach, this organ should be removed from the subject, everted and washed. This membrane will be found covered with a viscid fluid, and thrown into numerous rugse, and will ap- pear very different from that lining the oesophagus ; at the pylorus it forms a circular fold, [the phylosie valve] which is thin and floating ; external to this is a circular fasciculus of muscular fibres, which have a peculiar dense feel : this fold of mucous membrane narrows the opening into the duodenum, and when assisted by the surrounding muscular fibres, can perfectly intercept the passage from the stomach into the intestine ; in the cellular tunic, external to this membrane, particularly along the curvatures, are many small mucous glands, which open on the mucous surface ; these are the glandules Brunneri: the mucous coat of the stomach secretes the fluid called the gastric juice, which is generally believed to have the remarkable properties of being powerfully solvent and anti-putrescent. In the stomach the food undergoes the first important change in digestion, being here converted into a soft homogeneous pulpy mass, called chyme. [Cases have been recorded of double and even triple stomachs, in the human subject ; but this appearance is deceptive, and is merely the result of a contraction of the organ at one or more points of its cir- cumference, dividing it into separate compartments. The volume of the organ differs very much in different individuals, and in the same individual under different circumstances. The average capacity of the adult stomach in a medium state of distension is probably from DUBLIN DISSECTOR. 167 two to three pints ; this capacity however may be doubled, or tripled by distension: as compared with the inferior animals, the human stomach is smaller than that of the herbivorous, and greater than that of the carnivorous animals, which is one of the arguments in favor of the opinion that man is omnivorous. The lower part of the stomach sometimes presents a remarkably sacculated appearance without evidence of disease.] The duodenum is the next portion of the alimentary canal ; this is the first and shortest division of the small intestines ; it extends from the pylorus to the root of the mesentery, where the jejunum commences ; it lies partly in the right hypochondriac, and partly in the right lumbar and in the umbilical regions ; it takes a semicircular course around the head of the pancreas : this course may be di- vided into three parts ; the first, or superior transverse ; the second, or perpendicular, and the third or inferior transverse. The superior transverse portion ascends from the pylorus obliquely backwards and to the right side, beneath the edge of the liver, so as to touch the gall-bladder ; here the intestine makes a sudden turn, (the superior angle,) and the middle or perpendicular portion of it commences ; this descends in front of the right kidney, as low as the third lumbar vertebra, where it makes a second turn (the inferior angle) from which the inferior transverse portion ex- tends obliquely upwards, and to the left side, and at the first lumbar vertebra ends in the jejunum. The duodenum differs from the remainder of the small intestine, in being fixed in its situation, and being only partially covered by the peritonaeum, and being of much larger calibre, parti- cularly near the inferior angle ; its muscular coat is very strong, and the valvulee conniventes very numerous and large. The superior transverse portion is more contracted than any other part of it ; it is covered on both surfaces by the peritonaeum like the stomach, and is, therefore, more moveable than the rest of the intestine. The perpen- dicular portion is concealed by the omentum, and by the colon, and is covered by the ascending layer of the meso- colon; this portion lies on the right kidney, and on the vena cava, and has no peritonaeum posterior to it ; it is, therefore, fixed, and is dilatable ; the biliary and pancreatic ducts perforate the inner side of this division of the duo- denum ; these pass through its coats very obliquely, and open into the intestine, sometimes distinctly, and at other times conjointly, on a small papilla, opposite the inferior angle. The inferior transverse part of the duodenum passes across the aorta and the right renal vessels ; like the middle portion, it is only partially covered by the peri- tonaeum, being placed between the layers of the meso- 168 DUBLIN DISSECTOR. colon; its lower border may be seen without dissection, projecting through the inferior layer of the meso-colon ; the superior mesenteric vessels pass in front of the termi- nation of this part of the duodenum, and appear to com- press it against the aorta, so as to retard the passage of its contents into the jejunum. In the duodenum, the chyme is mixed with the biliary and pancreatic fluids, and a sepa- ration takes place between the chyle and the excrementi- tious part of the food. The jejunum and ileum intestines are covered by the omentum : if we raise this process and the arch of the colon, and place them on the edge of the thorax, the con- volutions of these intestines will be seen in the umbilical, hypogastric, and iliac regions ; convex anteriorly, concave posteriorly, and attached to the mesentery; the jejunum commences in the left lumbar, and the ileum ends in the right iliac region. There is no exact division between these two intestines ; the upper two-fifths are named the jejunum, and are placed higher in the abdomen than the ileum, which is the name given to the three remaining fifths. The jejunum is redder, feels thicker, and is larger than the ileum, which is pale and thin : these differences are striking when we compare the commencement of the jejunum with the terminating portion of the ileum ; in the intermediate space, however, they are gradually lost ; they depend on the greater vascularity and number of valvulae conniventes in the jejunum than in the ileum. The large intestine forms about one-fifth of the intestinal canal, and is subdivided into the ca3cum, colon, and rectum ; the large intestine differs from the small not merely in size, but in having a peculiar cellular and sacculated appearance, particularly when distended ; small processes also (the ap- pendices epiploicae) are attached along its whole course : three strong muscular bands, running in a longitudinal di- rection, may also be observed, chiefly in the caecum and colon, they appear to pucker the large intestine, so as to give it the cellular structure before mentioned : these bands, in addition to a muscular property, possess some elasticity also ; in some animals indeed they are decidedly elastic. The large intestines are paler than the small, and much thinner, having but few valvulse conniventes. The caecum, or caput coli, is situated in the right iliac fossa, in which region it is fixed by the peritonaeum, which in general covers it only anteriorly and laterally, while cellu- lar membrane connects it posteriorly to the iliac and psoas muscles ; in some, however, the peritoneum covers this pouch all round, and connects it to the iliac fossa loosely by a process named the meso-csecum; it is always covered DUBLIN DISSECTOR. 159 anteriorly by the abdominal muscles, and sometimes by the convolutions of the ileum ; it lies beneath the right kidney, and is continuous with the ileum and the colon. The caecum is somewhat triangular, the apex below, the base above at the colon, on its external surface are three irregular protu- berances, one anteriorly, and two posteriorly ; from its lower and posterior part a small tortuous process named app&idix vermiformis, about the size of a goose quill, hangs into the pelvis ; it is attached to and communicates with the caecum just below the ileum ; a sort of mesentery con- nects it in its situation : its use is not ascertained. [The position of the appendix is by no means invariable ; it some- times lies behind the caecum, extending up towards the liver, or else projecting beyond the caecum on its right side ; in other cases it lies behind the termination of the ileum, or even in front of it. Intestinal worms have been found in it and it is sometimes ulcerated.] The ileum joins the left or inner side of the caecum at a very acute angle ; it appears to perforate the latter, the pe- ritoneum and external muscular fibres of the ileum being continued into the corresponding parietes of the caecum, while the circular fibres and mucous coat of the ileum pro- trude into the caecum to form valves, as may be seen by opening the latter in a perpendicular direction, on the op- posite, that is, on the right side, and washing out its con- ' tents ; we then perceive the opening of the ileum, narrow, like a transverse slit, looking obliquely downwards and outwards, towards the right os ilii, and protected by two semilunar folds of mucous membrane, which enclose a few muscular fibres. The inferior fold, or ileo-ccccal valve, is the larger, is placed somewhat vertical, and secures the ileum against any matter re-entering it from the caecum ; the su- perior fold, or ileo-colic valve is smaller, and placed rather horizontal ; it secures the ileum against regurgitation from the colon ; these semilunar folds are united to each other at their extremities, (commissures^ and from each commissure a prominent fold is continued round on the inner side of the caecum ; these folds are called the frsena or retinacula of these valves, in consequence of which, and of the com- missures, the distention of the caecum closes the ileo-caecal foramen ; the caecum is provided with the same .longitudi- nal bands as the colon ; it has no valvulae conniventes. The colon extends from the caecum to the rectum ; it is di- vided into four portions, the right or ascending, the middle or transverse arch, the left or descending, and the sigmoid flexure ; there is, however, no mark of distinction whatever as to structure between these different divisions. The ascending colon extends from the caecum to the inferior 15 170 DUBLIN DISSECTOR. surface of the right lobe of the liver, which it marks with a superficial depression ; this portion of the colon is con- cave anteriorly, and covered by the peritonaeum and by the abdominal muscles ; it lies on the right kidney ; the duo- denum is connected to it internally ; the superior extremity is generally tinged with bile from being in contact with the gall bladder. The transverse arch of the colon extends tortuously from the right hypochondrium, across the inferior part of the epigastric or the umbilical region into the left hypochon- drium ; it is covered by the abdominal muscles, and lies anterior to the small intestines : on the right side it is con- nected to the liver, in the middle to the stomach and to the great omentum ; and its left extremity, which is superior and posterior to the right, is attached to the spleen by peri- toneum ; the appendices epiploicse are very numerous on this part of the colon. The left or descending colon extends from the spleen to the iliac region, is longer than the right, and is connected to the kidney and psoas by peritonaeum and cellular mem- brane. The sigmoid flexure is connected so loosely in the iliac fossa, that a great portion of it often lies in the pelvis : this part of the colon is partially covered by the small intes- tines, and connected to the psoas and iliac muscles, to the ureter and spermatic vessels. The rectum extends from the sigmoid flexure of the colon to the anus ; it commences opposite the left ilio-sacral arti- culation, and descends obliquely towards the middle line as far as the lower end of the sacrum : it then bends forwards towards the perinseum, and lastly turning downwards, it ends at the anus. The rectum is connected posteriorly to the sacrum and coccyx by the meso-rectum superiorly, and by vessels and nerves inferiorly ; anteriorly the rectum is connected to the peritonaeum above, and below, in the male subject, to the inferior fundus of the bladder, the vesicuke seminales, and the prostate gland: in the female to the uterus and the vagina : along the sides of the rectum is a considerable quantity of cellular tissue, and several vessels, particularly tortuous veins; inferiorly the levatores ani muscles cover the sides of this intestine, and its lower ex- tremity is surrounded by the orbicular and cutaneous sphincters. The rectum is separated from the bladder in the male, and from the uterus in the female by the cul de sac of the peritonaium, which may or may not contain some of the small intestine according to the state of the pelvic viscera ; the rectum, therefore, is only partially covered by the peritonaeum ; in the superior third this membrane co- DUBLIN DISSECTOR. 171 vers the intestine all around, forming the meso-rectum be- hind it ; in the middle third it is only connected to the fore part, and somewhat to its sides ; and to its inferior third it is wholly un-attached. The rectum is also sacculated like the colon, but the cells present a different arrangement in consequence of the peculiar disposition of the lining mem- brane ; it is found in general much dilated about an inch above the anus. In order to examine the structure of the intestinal canal, let the student remove the following portions of intestine, including each part between ligatures, having first distend- ed them with air ; a portion of duodenum, of jejunum near its commencement, of ileum near its termination, of the arch of the colon, and of the upper part of the rectum ; first, the duodenum possesses three coats connected to each other by cellular membrane ; the peritonseal or serous, the muscular and the mucous ; the first has been already men- tioned as giving but a partial covering to this intestine ; the muscular coat of the duodenum is formed of strong red fibres, which take a circular direction ; there are very few longitudinal fibres to be observed along it, except on the superior transverse portion : lay open a part of this intes- tine, and the internal mucous coat will be found, like that of the stomach, thrown into soft folds which lie nearly pa- rallel to each other in a circular direction ; these are named valvulse conniventes. Second, the jejunum and ileum also possess three tunics and intermediate cellular tissue ; the serous or peritonseal coat almost perfectly surrounds them except the small triangular space along the concave side where the vessels and nerves divide, and which space ad- mits of the more easy distention of the intestine ; the mus- cular coat is not so strong as on the duodenum, but more evidently consists of two sets of fibres ; the longitudinal are the most superficial, they are very pale and indistinct, ex- cept along the anterior or convex side of the intestine ; the circular fibres lie beneath these ; they are more distinct but also very pale : no fibre passes perfectly round the tube. The mucous coat is paler than in the stomach, and is thrown into numerous folds, particularly in the jejunum ; these folds are smaller and less numerous in the ileum ; the muscular coat in the latter intestine also is paler and weaker than in the former. The folds of mucous mem- brane, called valvulse conniventes, are larger in the jeju- num than in the duodenum or ileum ; in the first they will be found to be a quarter of an inch deep in some situa- tions; in others, however, much less; they form arches which encircle about three-fourths of the intestine, and end, some in a point, others are forked or pass off oblique- 172 DUBLIN DISSECTOR. ly into adjacent folds : these valves are of use in delaying the food in its passage along the canal, thus affording to the absorbents a better opportunity to imbibe all the nu- tritious matter of the chyle it may contain ; in proportion also as the intestine become distended, these valves be- come more tense, and project into the canal, so as to sepa- rate the food into smaller portions, and thus expose the en- tire mass to the action of the absorbents : on each of these valves are a number of small conical projections called vim : when these are examined through a magnifying glass, small pores are observable ; these are the mouths of the lacteal or absorbent vessels. Very small mucous glands are attached to the external surface of the mucous mem- brane of the intestine throughout its whole length ; larger glands may be noticed in different situations, some scatter- ed singly, others collected into clusters ; the former, or the glandule solitaries or Brunneri, are most distinct in the duodenum ; the latter, or the glandula aggregates or Peye- riy are most obvious in the ileum, particularly near its ter-. mination. Third, the large intestine, in some situations, as has been already observed, is but partially covered by peri- tonaeum ; this membrane is more loosely connected to the transverse arch of the colon than it is to the small intes- tine, and is un-attached along two triangular spaces, one along the concave border between the Iamina3 of the meso- eolon, the other along the convex, between the layers of the great omentum ; this circumstance favours the distention of the colon. The muscular coat of the large intestine also consists of longitudinal and circular fibres; the former, however, are collected into three fasciculi, all of which com- mence at the vermiform process, and pass along the ca3- cum and colon to the rectum : on this intestine the fibres separate, increase in thickness and number, and form a more perfect tunic ; near the anus these fibres are con- founded with those of the levator ani muscle of each side. The internal or mucous coat of the large intestine is pale, and forms but few and imperfect folds ; in the rectum it becomes more vascular and villous, and presents several longitudinal folds, as also three or four very remarkable, in a horizonal direction, these are so disposed, being at in- tervals and on opposite sides, as to convert the canal into a sort of spiral passage. As the food is propelled along the intestinal canal, the chyle is absorbed by the numerous lacteal vessels to which it becomes exposed ; it is also mixed with a quantity of fluid (succus intestinalis) secreted by the mucous glands, and by the vessels of the mucous membrane ; in the large intestine the food first presents the feculent properties, and in its passage along this part of the canal, DUBLIN DISSECTOR. 173 the absorbent vessels continue to take up any chyle that may have escaped the preceding, as well as the watery parts of the food. The peritonaeum and abdominal viscera present many morbid appearances. Peritonitis or inflammation of the peritonaeum is denoted by an increased and a reddish vas.- cularity of the membranes, a number of small red vessels can be distinctly seen ; it loses its transparency, and be- comes somewhat thick and pulpy ; the parietal and visce- ral layers are sometimes found agglutinated by coagulable lymph which also cements the several intestinal convolu- tions, but sometimes the cavity is filled with serous, or sero-purulent fluid, with shreds of lymph : peritonitis more frequently ends in some such eifusion than in the adhesive process, the contrary is more frequent in pleuritis ; peri- tonitis also sometimes exhibits gangrenous patches, but if it have been chronic, adhesive bands and false membranes are very apparent. In ascites or dropsy of this membrane, the tissue of the latter appears sound, sometimes remark- ably clear or pearly ; in this disease, some of the viscera, particularly the liver, are usually found in an anormal state. The omentum is sometimes the seat of general induration., or of particular tumours, adipose, sarcomatous and fungoid. The stomach may be the seat of an acute inflammation, or gastritis, the coats appear more thick and vascular than usual, and blood is sometimes seen effused between its tu- nics. Ulcers are frequently found in the stomach, of an oval or circular form, with thin and firm edges : indepen- dent of disease, the stomach not unfrequently presents considerable red patches on its mucous surface ; the coats are also sometimes nearly destroyed in some places, pre- senting a soft and ragged appearance ; this is caused by the gastric fluid digesting or dissolving the coats of the stomach after death. Both the cardiac and pyloric ends of the stomach are the frequent seat of cancer ; this principal- ly involves the mucous and muscular tissues, on the for- mer, large fungoid masses are thrown out which more or less constrict or obstruct the orifices of the organ, and im- pair its functions. The intestinal tube is subject to numerous diseases, in most of which the effects of inflammation are more or less visible : inflammation or enteritis is denoted by increased vascularity of the mucous surface and thickening of the tunics, in some cases the peritonaeum is also engaged ; the colour of the intestine is a deep or dark red ; acute inflam- mation sometimes ends in gangrene and effusion, sometimes in ulceration. The whole of the intestinal surface may bo 15* 174 DUBLIN DISSECTOR. the seat of ulceration ; in the small intestines, the ulcers are generally small, and are often found in the situation of the mucous glands ; in the large intestines the ulceration is usually in larger patches, and in cases of dysentery is of- ten very extensive. The intestinal tunics are occasionally the seat of malignant tubercle, which may obstruct the course of the contents of the tube ; of all parts of the in- testinal canal the rectum is most frequently the seat of scirrhus and its consequences. [The gastro- enteric mucous membrane, is of much importance in its pathology, and it is therefore necessary to understand fully its physiological state, as to thickness, consistence and color; the two former as a general rule are in direct ratio, but differ much in dif. ferent situations. The color also varies much in a state of health, as well as in disease. The entire thickness of the intestinal walls, is less in the lower part of the jejunum, the ileum, and the colon, than in the stomach, duodenum, upper part of the ileum and rectum. The thickness of the mucous membrane is greatest in the duodenum, and next in some parts of the stomach and rectum ; in the small intestines its thickness gradually diminishes, from the duodenum to the ileum, in the lower part of which it becomes very thin. In the large intes. tine, the mucous membrane is thin from its commencement until we reach the middle of the transverse portion of the arch, from which point it increases in thickness as far as the sigmoid flexure, where it is again thin, and lastly in the rectum, it is again nearly as thick as in the duodenum. The mucous coat of the stomach about the oeso- phagus, and in the great cul de sac, is thin, soft, and can only be sepa- rated in shreds, whereas towards the right side, and the pyloric ex tremity, it is from two to three times as thick, more resisting, and can be separated for a much greater extent : the gastro enteric mu- cous coat has no epithelium, this ending above at the termination of the oesophagus, and being again found below, near the verge of the anus. As already stated it is a general rule, that the consistence of this membrane is in direct ratio to its thickness ; this however is not true of the duodenum, where it is thickest, yet its tenacity is so slight that it can only be raised in fragments. The consistence is greater near the pyloric than the cesophageal portion of the stomach ; in the lower part of the jejunum and the ileum its consistence is greater than in the duodenum, while in the large intestine it is again less. The consistence throughout is greater in the adult, than in the fetus. The color of this membrane varies at different periods of life, and ap- pears to be deep, in proportion to the activity of the arterial develop- ment and circulation ; accordingly in the foetus and child, it is of a deep rose color, in the adult it is much whiter, and in the old subject it is of a greyish, or ash color ; again the color differs with the state of the system, being deeper in those in strong health, and of the san- guine temperament, than in others in whom the reverse obtains. The color also is affected by the process of digestion, by which it is changed from a pale pink or almost white, to a deep red almost vermilion hue, the intensity however depending upon the stimulating quality of the food used ; this change of color seems to affect the DUBLIN DISSECTOR. 175 stomach, duodenum, and upper part of the jejunum, while the other portions of the canal are but little altered. The color of the gastro- enteric mucous membrane, depends also upon the kind of death. In those who have died of long continued diseases, it is apt to be of a pale blanched appearance ; in persons who die suddenly and from violence, as hanging, drowning &c., it is found of a deep red color. Lastly the color is affected by different substances taken into the stomach, as infusion of logwood, spirits of lavender, nitrate of silver &c., the two former cause a deep red color, the latter a greyish or slate color. There is also a post mortem redness, of the membrane, depending, upon the accumulation of blood at the more dependent parts. All these facts are of importance in legal medicine. The submucous cellular tissue is so distinct and developed, that it deserves to be con- sidered as a proper tunic, the third coat of the stomach and intes- tines ; it gives great strength and resistance to the organs, and serves as a skeleton for the attachment of the muscular fibres ; this coat is very distinct in the purely carnivorous animals, the vessels ramify upon this tunic, before being distributed to the mucous membrane, and the muciparous glands are imbedded in it, although they open upon the surface of the lining membrane. These follicles are more fully developed in children than in adults, and in preparing them may be rendered more distinct by the application of warm vinegar. The single follicles are larger in the duodenum, than in the stomach, in the rest of the small intestines, they are also larger, than in the stomach, but smaller than in the duodenum, or large intestines. The glandules agminate of Peyer, or elliptical plates as they are called from their form, are almost confined to the lower half of the ileum, and vary in number from eighteen to twenty-five ; they also vary in size, being from half an inch, and even a fourth, to two inches in length, and from two or three to ten lines in breadth, they are always found along the convex edge of the intestine opposite the attach- ment of the mesentery, and are entirely wanting in the large intes- tine. These organs are supposed to be physiologically different from the solitary follicles, because they present certain pathological differ- ences. The plates are found enlarged, prominent, and even ulcerated in phthisis, typhus fever, and scarlatina maligna. The intestines may communicate with the cavity of the peritoneum, either by per- foration or laceration, the former of which is the result of ulceration of the coats, the latter of external violence, and may occur without any external marks upon the abdomen : the parts most liable to la- ceration, are the jejunum and upper part of the ileum. Any of the viscera of the abdomen may be involved in a hernial tumour, but most commonly the omentum, or the lower part of the small intestine is protruded. The small and large intestines are both the seat of in- tussusception, but the ileum is most liable to it ; its extent varies from an inch or two to even three feet, and sometimes the invaginated por- tion sloughs off and is discharged. There is one form of this affec- tion, which appears to occur in articulo mortis, presenting no signs of inflammation ; there may be from one to twelve of these displace- ments in the same subject, and it may occur in either direction. Earthy concretions, are sometimes found in the alimentary canal, of 176 DUBLIN DISSECTOR. the human subject as well as of inferior animals ; they vary in size from that of a pea to that of an orange, and one case is recorded in which the body weighed four pounds ; the number also varies, there being generally but two or three, but sometimes ten or fifteen, they usually exhibit a central nucleus. In the college museum there are two specimens from the inferior animals, (presented by Dr. Sabine of this city, who has a very choice private collection of Morbid Ana. tomy and Natural History,) one of which taken from the stomach of a liorse has for its nucleus, what appears to be a bit of corn cob, its diameter is about four inches, it is formed of concentric laminae, looks like marble and receives a high polish. The hair balls found in the stomach of the ox, appear to be formed by an accumulation of hair coated over with numerous layers of concrete mucus, which form a complete capsule. In post mortem examinations of the abdomen, some portion of the intestine, is often seen very much contracted, so as almost to oblite- rate its cavity and yet no evidences of disease are present, this occurs in coils of the small intestine but more often in the large, in the fol- lowing order as to frequency, the left part of the transverse portion of the arch of the colon, the descending portion, the sigmoid flexure, and the upper part of the rectum. This condition appears to depend upon the close contraction of the muscular fibres upon the empty in- testine. Hemorrhoids, prolapsus ani, fissura ani, and fistula in ano, are all diseases occuring in the lower part of the rectum, and about the anus. Intestinal worms, of different kinds, may be found in the alimentary tube, at almost any point between the mouth and the anus. The existence of worms in the cavity of the peritonaeum with- out perforation or laceration, was demonstrated to me a year since, in the post mortem examination of a horse, which died of acute pleuritis. These worms were found principally on the peritoneal covering of the liver, but were moving freely in the cavity ; there- were from ten to fifteen of them varying in length from two and a half or three, to six inches, and from one to two lines in diameter. There was no evidence of disease about the peritoneum; lam not aware that any thing of this kind has been seen in the human sub- ject. Anomalies not unfrequently occur, in the development of the alimentary canal, and many of them are analogous, to the natural conformation of inferior animals. The large intestines are sometimes entirely wanting, the ileum ending in a blind cul de sac ; sometimes the rectum only is wanting, at others, the anus is simply imperforate. The rectum sometimes terminates in the bladder, in the vagina or in the urethra ; in a case of the latter kind which occured in a male child, the subject lived one year, and then died from inflammation arising from neglect of the parts. The vermiform appendix is some- times entirely wanting, and not unfrequently the small intestines pre- sent processes or blind canals, from one to three or four inches in length.] The glandular viscera of the abdomen which are subser- vient to digestion are the liver, spleen, and pancreas. The liver is the largest secreting gland in the body ; it fills the right hypochondrium, extends though the anterior DUBLIN DISSECTOR. 177 part of the epigastric region into the left hypochondrium as far as the cardiac orifice of the stomach, beyond which, however, it frequently extends, even to the spleen ; it is sit- uated below the diaphragm, and above the right kidney, the stomach, duodenum, and lesser omentum ; it is support- ed in this situation by several folds of peritoneum, termed ligaments of the liver, viz. the falciform, round, right, left and coronary ; these connect it to the diaphragm and ab- dominal muscles, and the lesser omentum attaches it to the stomach and duodenum. The suspensory or falciform ligament is a fold of perito- neum attached anteriorly by its convex border to the linea alba, to the rectus muscle of the right side, and to the dia- phragm; it passes obliquely backwards and to the right side, and is attached by its posterior or concave edge to the upper or convex surface of the liver, on which its laminae separate, and expand over each side of this organ ; en- closed in the inferior edge of this fold is the obliterated umbilical vein, which substance in the adult is named the ligamentum teres : this which is enumerated as the second ligament of the liver, ascends from the umbilicus, obliquely backwards, and to the right side, and is inserted into a notch in the thin or anterior edge of the liver, which notch is the commencement of the umbilical or horizontal fissure of the liver. The right and left lateral ligaments are trian- gular folds, connecting the right and left lobes of the liver to the diaphragm : the left lateral ligament lies anterior to the cardiac orifice of the stomach : the right lateral liga- ment is directly above the right kidney. The coronary lig- ament is situated at the upper extremity of the falciform process, and consists of two laminse of peritoneum, which separate from each other, and connect the superior thick edge of the liver to the diaphragm ; between the laminse of this process the liver is deprived of a serous covering, and is in contact with the diaphragm ; this space lies anterior to the inferior vena cava. The liver is of an irregular form ; it is longer transversely than from before back- wards ; its posterior edge is very thick, and in contact with the diaphragm ; its anterior edge is thin, convex, and on a level with the edge of the right hypochondrium, and with the lower part of the epigastric region ; two notches may be observed in this edge ; one below the falciform ligament, into which the round ligament or obliterated umbilical vein enters, the other corresponds to the gall bladder. [The size and weight of the liver are very much affected by dis- ease, and by the state of its own circulation, which also affects its color. In a state of health its average weight is from three and a quarter, to four and a quarter pounds : the transverse diameter is from 178 DUBLIN DISSECTOR. fen to twelve inches, the antero-posterior from six to seven, and the thickness at the centre and posterior edge from two and a half to three and a half. The color of the organ varies with the amount of blood in it, thus in the foetus the organ is very vascular and of a florid red, in the adult it is of a reddish brown color, with blue or black spots, on the anterior margin and inferior surface ; in persons who have been hung, it is said to be of a deep pink, or even purple, and in simple conges- tion it is of a florid red. The volume of the organ varies with its own circulation, thus it is very large if there be an obstruction to the return of the blood to the heart. It is also proportionably very much greater in the foetus and new born infant, than in the child or adult ; thus it is said that in the foetus of three weeks, the weight of the liver is equal to half that of the whole body, at the full term to one eigh- teenth, and in the adult, to one thirty-sixth.] The superior or anterior surface is smooth and convex, and divided by the suspensory ligament into a right and left portion, and is contiguous to the diaphragm. The inferior surface is very irregular, marked by several pro- jections and depressions ; the former are called lobes, and are five in number, viz. first, the great or right lobe ; second, the left, separated from the former by the horizontal fis- sure ; third, the Spigelian or middle lobe ; this is situated be- hind the lesser omentum, and above and behind the trans- verse fissure, and between the oesophagus and the cava ; it is connected to the right lobe by two roots ; one is thin and placed vertically between the fissure for the vena cava and that for the ductus venosus ; the other is thick and placed transversely, and is called lobulus caudatus, or the fourth lobe of the liver ; the lobulus caudatus is immediately be- hind the transverse fissure, and extends from the Spigelian, along the right lobe between the depressions marked by the colon and right kidney. Fifth, the lobulus quadratus or anonymus, is at the anterior part of the right lobe, in front of the transverse fissure, and between the gall bladder and horizontal fissure. The principal depressions or fissures on the inferior surface of the liver are the following : first the transverse fissure which is situated between the lobulus quadratus and caudatus, and extends from the horizontal fissure transversely to the right ; the vessels and nerves of the liver enter the gland in this fissure ; second the horizontal fissure extends from the notch in the anterior edge of the liver, backwards and upwards between the right and left lobes ; the anterior part of this fissure contains the ob- literated umbilical vein, the posterior part the obliterated ductus venosus ; third, the fissure for the vena cava is between the lobulus Spigelii and the right lobe ; this, at the ante- rior part of the horizontal fissure, is frequently like a DUBLIN DISSECTOR. 179 foramen in the liver, being surrounded by the substance of the gland : fourth, the depression for the gall bladder is on the inferior surface of the right lobe, and to the right side of the lobulus quadratus ; the substance of the liver is sometimes deficient over this bag ; fifth and sixth, super- ficial depressions on the under surface of the right lobe ; the anterior corresponds to the colon, the posterior to the right kidney and its capsule ; these depressions are indis- tinctly marked in some subjects ; they are separated from each other by the extremity of the lobulus caudatus ; seventh, a superficial depression on the under surface of the left lobe, corresponding to the anterior surface of the stomach ; eighth, a broad notch in the posterior edge of the liver, corresponding to the spine and to the right crus of the diaphragm ; the venae cavse hepaticse leave the liver in this situation. The liver is of a peculiar brown colour, interspersed with yellow; in some subjects it is much darker than in others : in the very young it is red and soft, and in the old it is generally pale and yellow, and often hard and brittle ; it has two coats, a serous and fibrous ; the serous or peritonseal tunic covers the whole surface of the liver, except in those situations where the vessels, either pervious or obliterated, are situated, and between the laminse of the corronary ligament, also in the depres- sion in which the gall bladder is lodged. The second, or fibrous coat, is the immediate capsule to the gland ; it is thin, little more than condensed cellular membrane ; it is most distinct and strong where the serous coat is deficient ; it covers the whole surface of the liver, and adheres to it by innumerable shreds or processes, which pass into its substance; it also accompanies the three vessels of the liver which enter or leave the transverse fissure, and forms a capsule or sheath around their ramifications throughout the entire organ; this sheath receives the name of the capsule of Glisson; it surrounds the vessels very loosely, and also encloses loose cellular tissue ; hence it is, that if these vessels be divided by a perpendicular incision through the liver, they will be found to collapse and recede ; where- as, if the venae cavse hepaticse, which run from the thin towards the thick edge of the liver, be divided by a trans- verse incision through the liver, they will not recede or collapse, but remain perfectly open, in consequence of the absence of this sheath, and of their close adhesion to the substance of the gland. The structure of the liver con- sists of numerous small granulations of a brown and yel- low colour, connected together by the branches of the he- patic arteries, veins, and ducts ; these grains are called acini of the liver, in each of them a branch of the hepatic 180 DUBLIN DISSECTOR. artery and vena portarum terminate, and out of each proceed a branch of the hepatic veins and ducts. Through the liver, therefore, four sets of vessels ramify, in addition to numerous lymphatics, viz. the branches of the hepatic arteries, vense portarum, hepatic ducts and hepatic veins : the venas portarum are supposed to be the vessels from which the bile is secreted ; the hepatic arteries nourish the substance of the liver ; the hepatic ducts carry the bile from this organ, and the vense cavas hepatica3 return the blood which has circulated through the liver, to the inferior vena cava, just as this vessel is passing through the dia- phragm. The vena cav& hepatica, three or four in number, are seen escaping from the liver at the superior thick edge, behind the coronary ligament, and immediately joining the inferior or ascending vena cava. The three other vessels of the liver may be seen between the layers of the lesser omentum, the artery lying to the left side, the biliary duct to the right, the vena portarum behind and between both ; the artery and vein descend obliquely inwards towards the spine, behind the pancreas. The hepatic artery is a branch of the coeliac axis, and the vena portarum commences in front of the last dorsal vertebra, and behind the pancreas, from the confluence of the splenic and mesenteric veins The right and left hepatic ducts, on clearing the transverse fissure, unite and form the hepatic duct, which descends for about one inch and a half along the right side of the les- ser omentum, and is then joined by the cystic duct, from the gall bladder : the union of these forms the ductus corn- munis choledochus ; this vessel, about three inches long, descends vertically behind the pylorus, the upper part of the duodenum arid the pancreas, and is imbedded in the substance of the latter, about, the middle of the internal or concave side of the middle division of the duodenum, this duct perforates the coats of this intestine in a very oblique direction, and opens on a small papilla internally, opposite the lower angle of the duodenum : as the ductus choledo- chus is about to perforate the duodenum, it is in general joined by the duct from the pancreas. No viscus in the abdomen presents such frequent and varied morbid appearances as the liver ; acute inflammation, or hepatitis is but rarely met in the dead body ; it is denoted by a deep red or purple colour, a firm, heavy feel, and in the opinion of some, by an increase of size ; the investing capsule is easily detached, and the parenchyma appears very granular and vascular: inflammation may end in suppuration, which, in general, is collected into a very large abscess, the contents of which may have been dis- charged into the colon, the stomach, or some of the intes- DUBLIN DISSECTOR. 181 tines ; abscess of the liver also sometimes points external, ly, and in some rare cases, opens into the cavity of the pleura, or into some of the bronchial tubes. The liver is the seat of different sorts of tubercles, viz. small and dif- fused, large and circumscribed, scrofulous, scirrhous, fun- goid, hydatid, melanotic, &c. : hydatid cysts containing several small hydatids are not uncommon in this organ. [The liver is also liable to hypertrophy and atrophy, which are usually connected, with either an indurated or a softened state of the organ ; it is also the seat of a fatty degeneration, and occasionally the worm called liver fluke is found in it, but much more frequently in inferior animals ; it is also the seat of scirrhosis, in which disease it presents a tuberculated or nutmeg like appearance ; cartilaginous and osseous depositions are also found.] The gall bladder is situated in the right hypochondrium in a depression on the inferior surface of the right lobe of the liver : this membranous sac is of a pyriform figure ; the large extremity or fundus being directed forwards and downwards ; in some persons it projects below the liver against the abdominal muscles ; it is generally contiguous to the pylorus and to the colon ; the smaller extremity or neck of the gall bladder is directed upwards, backwards, and inwards, is a little convoluted, and ends in the cystic duct, which is about an inch and a half long : this duct bends downwards and inwards, and joins the hepatic duct at an acute angle, the union of which forms, as was before mentioned, the ductus choledochus. The gall bladder is closely united to the liver by the peritonseum, which pass- es over it; also by cellular membrane and small blood- vessels ; it is composed of a partial serous and a perfect cellular coat, and is lined by a mucous membrane; the latter has a peculiar honey-comb-like appearance, and in the duct is disposed in a spiral lamina ; there is no appear- ance of a muscular coat. This viscus serves as a reservoir for the bile, when this fluid is not required in the intestinal canal. The bile is secreted in the liver, and flows down the hepatic duct, and if not required in the duodenum, or if obstructed in the ductus choledochus, it passes into the cystic duct to the gall bladder, where it resides a longer or shorter time, during which period its watery part is absorb- ed ; at the end of some time, when the bile is required to assist in digestion, it is forced out of the gall bladder, and then flows again along the same cystic duct to the ductus choledochus, and so to the duodenum. The bile is not secreted in the gall bladder, nor can it possibly enter or leave this viscus by any other channel than through the cystic duct. The morbid appearances observed in the gall bladder are, T82 DUBLIN DISSECTOR. great distention, in consequence of obstructed ductus cho- ledochus, or almost total obliteration of its cavity in con- sequence of obstructed cystic duct. This viscus also fre- quently contains biliary calculi ; when there is but one calculus it is usually large and of an oval form, and either fills the cavity, or partly obstructs the duct ; there are frequently several calculi present, in this case they present every variety of form and size, as also several smooth sides and angles, the probable effect of rubbing against each other. The spleen is situated in the left hypochondrium, between the stomach and ribs, beneath the diaphragm, and above the kidney and the colon ; it is in contact with and connect- ed to the diaphragm by the peritonaeum, also to the stomach and pancreas by vessels and by the peritonaeum. The spleen is somewhat ovaf; convex towards the ribs, and concave towards the stomach ; on the latter surface there are sever- al holes, and about the centre of it a depression or fissure for the entrance and exit of blood vessels ; all this surface, however, is not concave, the part anterior" to the vessels only being so, while the part posterior to them is convex ; the colour of the spleen is somewhat purple or livid; it is covered by peritonaeum, and beneath this by a fibrous cap- sule, which invests its entire surface, and also passes into its substance along with the blood-vessels, and assists in forming the cells of which this organ is composed : these cells are found to contain a quantity of blood, partly co- agulated ; also a number of small grains, which may be separated by maceration, but the nature of which is not well understood ; the spleen has no excretory duct. The exact use or function of this viscus is not yet ascertained ; sometimes two or more small bodies, of the same colour and structure as the spleen, are found in its vicinity, be- tween the laminse of the omentum. [The color of the spleen varies from a pale grey to a dark brown, or deep blue, it is influenced by disease, age, and the kind of death. In the recent subject it is of a light blueish shade, which soon changes to a deep purple, especially on exposure to the air. Its weight is variable even in a state of health, rarely exceeding eight ounces, it is sometimes as much as fourteen, and then again as low as two. It also varies much in volume, in the majority of cases however, its length is from four and a half to five inches, its width from two and a half to three, and its thickness one and a half ; its volume is pro- portionably greater in man than in other animals, and in the adult, than in the foetus, its volume seems also to depend upoiv its own cir- culation in connection with the process of digestion. Supernumerary spleens sometimes exist, but there are rarely more than one or two of them ; still cases are reported in which there have been seven, ten, and even twenty ; they are found in the oment'tra gastro-flplenicum, DUBLIN DISSECTOR. 183 and are about the size of a nutmeg, many animals have more than one spleen.] The spleen is not often found diseased ; the greatest possi- ble variety as to size and consistence is observed, without any morbid change ; in some cases it is so soft as to break under the slightest pressure : its coats are subject to thick- ening and induration, cartilaginous and even bony tuber- cles or patches are very common occurrences in its fibrous capsule. The pancreas lies behind the stomach, and may be exposed by dividing the great omentum below the stomach, and rais- ing the latter organ towards the thorax. This conglomerate gland is of great length, about seven inches long, and about an inch and a half broad. [And its medium thickness is six lines, it is however thicker at its right than its left extremity. Its volume is proportionally greater in the foetus and child than in the adult. Its color varies with age, in children, it is of a rosy tint, in adults lighter, and in old age of a pale yellowish hue.l It extends from the lower part of the left hypochondriac and epigastric regions, obliquely downwards and forwards into the umbilical region, where it is surrounded by the duo- denum ; it is covered by the stomach and the ascending layer of the meso-colon; it lies anterior to the left cms of the diaphragm, the vena portarum, and the aorta, and over- laps the concave border of ,tke duodenum, to which it ad- heres very closely. The splenic or left extremity (its tail) is small, compared with the right, which is broad and flat, and is named the head ; the anterior surface looks a little upwards, the inferior edge being raised forwards by the su- perior mesenteric artery and vein, which pass behind it ; a groove may be remarked on the posterior and upper part of the pancreas ; this contains the splenic artery and vein. The pancreatic duct may be seen by scraping off a little of the posterior surface of the gland about its centre. This duct is remarkably white and thin ; it commences in the small extremity of the gland, and extends to the large end, receiving in its course numerous branches on each side ; it usually joins the ductus choledochus ; it sometimes, how- ever, opens into the duodenum distinctly ; attached to the head of the pancreas there is sometimes a glandular mass of the same structure as the pancreas, and opening by a small vessel into the pancreatic duct ; this is named the lesser pancreas. The pancreatic fluid is supposed to be of use in diluting the bile, and rendering it and the contents of the duodenum more miscible with each other. The struc- 184 DUBLIN DISSECTOR. ture of the pancreas is similar to that of the salivary glands, and is thence called by some, the abdominal salivary gland The pancreas is not" often found in a morbid state., indura- tion of its structure and calculi in its duct may be occasi- onally noticed. OF THE VESSELS AND NERVES OF THE ABDOMEN. THE abdominal aorta gives off three large branches to supply the organs of digestion, viz. the coeliuc axis, the su- perior mesenteric and inferior mesenteric arteries. The c&liac axis may be seen by tearing through the lesser omen- tum above the lesser curvature of the stomach, to arise from the forepart of the aorta, at the upper edge of the pancreas ; it is about half an inch long, and divides into three branches, viz. the gastric, hepatic, and splenic ; the gastric artery and its branches run between the laminae of the lesser omen- turn, along the concave edge of the stomach, and supply both surfaces of this organ. The hepatic artery accompa- nies the vena portarum and the biliary duct to the trans- verse fissure of the liver, first sending off a small branch to the pylorus (pylorica superior,) next a large branch (gastro-duodenalis,) which descends behind the pylorus and subdivides into two branches, the pancreatico-duode- nalis and gastro-epiploica dextra ; the former supplies the pancreas and duodenum ; the latter runs along the convex edge of the stomach, between the layers of the great omen- turn ; the hepatic artery then divides into the right and left hepatic arteries, which supply the right and left lobes of the liver ; the right hepatic is the larger, and gives off a small branch, arteria cystica, to the gall bladder. The splenic artery is the longest and largest branch of the coeliac axis ; it passes along the upper and posterior part of the pancreas, to which it gives many branches ; near the spleen it sends off the gastro-epiploica sinistra, which runs along the convex edge of the stomach, between the layers of the great omentum ; the splenic artery then divides into five or six branches, which enter the foramina in the concave sur- face of the spleen : from these splenic branches five or six small arteries, the vasa brevia, pass to the left or great end of the stomach. The superior mesenteric artery arises about half an inch below the cceliac axis, behind the pancreas ; it descends in front of the duodenum, enters the mesentery, and bends obliquely towards the right iliac fossa ; from its left or convex side it sends off sixteen or eighteen branches, which supply the jejunum and the ileum, and from its con- cave or right side arise three branches, the ileo-colica, co- lica dextra, and media ; these arteries supply the corres- DUBLIN DISSECTOR. 185 ponding portions of the colon, and inosculate with each other. The inferior mesenteric artery arises a little above the division of the aorta into the iliac vessels ; it descends into the left side, and divides into three branches. First, the co- lica sinistra, which supplies the left lumbar colon, and in- osculates with the colica-media ; second, the sigmoid ar- tery, which supplies the sigmoid flexure of the colon ; and third, the superior hsemorrhoidal, which is distributed to the rectum. These arteries are accompanied by corres- ponding veins, which all unite to form the vena portarum ; the inferior mesenteric vein accompanies the artery of that name to the aorta, and there joins the superior mesenteric -vein, which is a very considerable vessel; this common trunk then ascends behind the pancreas, and is joined by a very large vein from the spleen ; the confluence of the splenic and mesenteric veins forms the commencement of the vena portarum; this vessel ascends obliquely to the : right side, surrounded by nerves and cellular membrane, .-and enclosed in the lesser omentum ; near the transverse fissure it becomes dilated (the sinus of the vena portarum) and then divides into the right and left branches ; the former is ^he larger, the latter the longer of the two ; each branches out through the liver, surrounded by the capsule of Glisson, .and runs in a transverse direction : injection shows their : minute branches to communicate in the acini with the pori biliarii, or with 'the, commencements of the hepatic ducts. The nerves which supply the digestive organs are the : eighth pair, and the splanchnic branches, from the sympa- thetic.: the eighth pair descend along the oesophagus, and ; are distributed almost wholly to the stomach ; some few branches pass along the lesser omentum to the liver. The splanchnic nerves are two in number, a right and left ; they .are each formed by filaments from the dorsal ganglions of the sympathetic nerve, in the thorax ; they enter the ab- g^g 4. Acceleratores Urinaa or Ejaculatores Seruinis, $ 5. Transversales Perinaei, 6. Levatoren Ani, Vide p. 203. 7. Compressores Urethrse, " " 204. 8. Coccygei, " " 208. PLACE the subject on the back, bend the thighs and knees upon the trunk, and secure them in the same position as if you were about to perform the lateral operation of litho- tomy ; the dissection will be fasciliated if the pelvis be raised by a block placed beneath it ; moderately distend the lower end of the rectum with sponge or curled hair ; introduce a staff or catheter into the urethra and bladder ; secure the penis to it by a ligature, and raise up the scro- tum. The perinaum extends from the os coccygis behind, to the arch of the pubis before ; is bounded on each side by the rami of the pubis and ischium, by the tuber ischii, and by the great sacro-sciatic ligament, which extends from 198 DUBLIN DISSECTOR, that process to the side of the sacrum and coccyx ^ the glutseus maximus overhangs this ligament ; the tuberosity and ramus of the ichium can be felt through the integu- ments, also (unless the subject be very fat) the rarnus of the pubis leading obliquely upwards on each side to the symphysis: the integuments of the perineum and scrotum are generally of a dark brownish colour in the adult, and of a reddish hue in the child ; very thin around the anus, and covering the scrotum, but dense in the intermediate space : along the mesial line, a prominent hard ridge is ob- servable, the raphe of the perinseum ; this line commences in front of the anus, and extends along the perineeum, scrotum and penis, as far as the prepuce of the latter. Dissect off' the integuments from this region, and we ex- pose posteriorly a cutaneous muscle (the sphincter ani) sur- rounding the anus, and anteriorly a stong fascia covering the muscles of the perinseum, the crura penis, and the cor- pus spongiosum urethrre. SPHINCTER ANI is flat, thin, oval, pale, and open in the middle ; it arises from a ligamentous substance, which ex- tends from the os coccygis to the rectum ; the fibres de- scend obliquely forwards, expanding on either side nearly as far outwards as the tuberosity of the ischiurn ; at the posterior part of the anus this muscle divides into two fas- ciculi ; which pass, one at each side of this opening, and unite at its anterior part, thus encircling this orifice ; insert- ed into the raphe in the integuments, and into the superfi- cial fascia ^ a fasciculus of it also perforates the latter, and is inserted into the common central point of the perinseum ; a point which will be more fully seen when the fascia shall have been raised; Use; to close the anus; it may also draw downwards the bulb of the urethra; this muscle is almost constantly in a state of contraction, and, like all the sphincter muscles, belongs to the class of mixed muscles. One of its surfaces looks downwards, and is superficial, the other looks upwards, and is connected to the levatores ani muscles; one edge is internal, the other external. It is superficial ; its lateral extent is much greater in some sub- jects than in others:; a few of its external fibres are di- vided in the first incision in the lateral operation of litho- tomy ; beneath and internal to this muscle we may expose the following, with very little dissection. SPHINCTER INTERNUS vel OREICULARIS, consists of a thick, but pale fasciculus of muscular fibres, which encircles the lower extremity of the rectum, having no attachment to the coccyx behind, and but a slight one to the central point before : it is in close contact with the mucous membrane of the intestine ; its use is similar to that of the last des- DUBLIN DISSECTOR. 199 cribed muscle. Its surfaces are internal and external, its edges superior and inferior. Anterior to, and on each side of the anus, we find beneath the integuments a condensed cellular texture, covering the other muscles in the peri- nseum ; this is the superficial fascia ; it is continued from the inner side of one thigh across the perinseum to the opposite, adhering to the rami of the ischium and pubis on each side, by tendinous fibres ; this fascia is very dense about the middle of the perinseum ; posteriorly, on either side of the anus, it is loaded with soft, large-grained, adi- pose substance : anteriorly it extends over the scrotum, and becomes -thin and fine, like reticular membrane, and continuous with the superficial fascia from the abdomen. This fascia covers the vessels, and all the muscles of the perineum, except the two sphincters of the anus. Separ- ate this fascia from one side of the perinseum, and reflect it towards the opposite ; its density and close connexion to the lateral boundaries of this region will then become ob- vious ; a number of veins and nerves, and a quantity of fat also will be observed ; when the latter is dissected away, those muscles of the perineum, which are attached to the penis and urethra, will appear, covered, however, by a fine but dense aponeurosis, which may be next dissected off; these muscles are six in number, three on each side, viz. the erector penis, transversalis perin^i, and accelerator urina?.* If the perinasum be divided by a transverse line drawn from one tuberosity of the ischium to the other, into an anterior and posterior part, we shall find that the ante- rior triangular space, or the ureihral region, contains in the male subject the six muscles just named, also the crura penis and the corpus spongiosum urethrse : the posterior triangular division, or the anal region, contains the lower extremity of the rectum, surrounded by the cutaneous and deep sphincters, also on each side of this intestine a con- siderable quantity of fat, filling up the space between the side of the rectum and the obturator internus muscle and fascia; this, the ischio-rectal space, is bounded superiorly, that is, separated from the pelvis by the levator ani mus- cle, and inferiorly is closed by the fascia and integuments ; the fat is from two to three inches in depth ; when this mass is dissected out of the space which it fills, the levator ani muscle, covered by the ischio-rectal layer of the pelvic fascia, [or the deep perinatal fascia] will be seen extended from the internal surface of the pelvis to either side of the rectum, and to the coccyx, so as to form a partition be- * A knowledge of these fasciae will explain the resistance which this structure presents to collections of urine or of pus from coining to the surface. 200 DUBLIN DISSECTOR. tween the pelvis and the perinseum. First examine the muscles in the anterior part of the perinseum ; the erector or compressor penis is most external, and lies on the crus penis ; the accelerator urinoe extends along the middle of the perinaeum, attached to its fellow along the raphe, and covering the urethra; the transversalis perinsei connects the posterior extremities of these muscles. Immediately in front of the rectum, in the middle line, and behind, but connected to the bulb of the urethra, is a small, white, ten- dinous spot, composed of condensed cellular tendinous and muscular substance ; into this many of the perinseal mus- cles are inserted ; it is, therefore, called the central point of the perinseum, or the common point of insertion to the mus- cles of the perinseum. ERECTOR, or COMPRESSOR PENIS, long and flat, narrow at each extremity, broader in the middle, arises tendinous and fleshy from the inner surface of the tuber ischii, and from the insertion of the great or inferior sacro-sciatic ligament, the fibres proceed forwards, upwards, and inwards, adher- ing to the edges of the rami of the pubis and ischium, and covering the crus penis. The fleshy fibres terminate in a tendinous expansion, which inclines forwards, upwards, and outwards, and is inserted into the fibrous membrane of the corpus cavernosum or crus penis. Use ; to draw down the penis ; it also contributes to the erection or distention of this organ by propelling the blood into it, and by the compression of the veins against the bone preventing the free return of this fluid through these vessels : it is the most exteinal of the muscles in this situation, it covers and ad- heres to the crus penis. ACCELERATOR URINJE, or EJACULATOR SEMINIS, is in the middle of the perinaeum, extends from the front of the rec- tum to the back part of the scrotum, and is attached to its fellow along the mesial line ; it arises first, by tendinous fibres from the triangular or inter-osseous ligament, inter- nal to the erector penis; secondly, by a broad tendon, which is common to the opposite muscle, and which lies above the urethra, between it and the pubis ; thirdly, more anteriorly by a tendinous expansion from the side of the corpus cavernosum penis. The posterior and middle fibres descend inwards ; the anterior fibres, which are longer, descend obliquely backwards and inwards ; all the fibres are inserted along with those of the opposite muscle into the middle tendinous line or raphe of the perinaeum, which ex- tends from the common central point to the back of the scrotum. Use; to expel the last drops of urine and semen, also to distend the corpus spongiosum urethrae by propel- ling the blood into its cells. The posterior origin of this DUBLIN DISSECTOR. 201 muscle is overlapped by the erector penis, and by the per- inseal vessels and nerves ; some of its fibres extend in some cases outwards, as far as the ramus of the ischium, and arise from the bone ; the origin of the middle fibres lies above the urethra, and that of the anterior is external to the crus penis. The anterior fibres of this pair of muscles, by converging towards the middle line, resemble the letter Y. The accelerators urinas muscles fill up the middle of the perinseum, cover the bulb, and encircle the urethra an- terior to it. Separate these muscles from each other along the mesial line, and detach one of them from the corpus spongiosum urethree ; then by examining its deep surface, its origin, particularly that which lies above the urethra, anterior to the bulb, will be more distinctly seen. TRANSVERSALIS PERIN^EI, is thin and weak, often indis- tinct, and sometimes wanting ; it arises from the inside of the tuberosity of the ischium, above the erector penis mus- cle, the fibres pass transversely inwards and a little down- wards, and are inserted into the central point of the perin- reurn, behind the accelerator urinae muscle. Use, to fix the central point, and support the anus ; it may also dilate the bulb. This muscle is covered by the sphincter ani, and by the superficial fascia, a small artery (transversalis perinsei) runs along its anterior edge ; it lies on the levator ani, is connected to it by cellular membrane, and in some cases is intimately joined to it. In some subjects a second mus- cle may be observed taking a transverse course (the trans- versalis alter ;) this arises from the ramus of the ischium, proceeds obliquely forwards and inwards, and is inserted into the accelerator urinse. The transverse perinsei mus- cles are very irregular in size in different persons, in some being found very distinct and strong, in others a few pale and scattered fibres only point out their course and situa- tion : the dissector is frequently obliged to cut oft' a few fasciculi from the levatores ani muscles, to make even an appearance according with the description given in books. Between the three last described muscles on each side, we may remark a triangular space, which is bounded exter- nally by the crus penis and the erector penis muscle, in- ternally by the urethra and accelerator urina3 ; the base is posteriorly, and is formed by the transversalis perinsei muscle. This space contains a quantity of fat, also the perinatal artery, veins, and nerves, branches of the pudic vessels and nerves ; into this space, on the left side of the perinseum, the operator must sink his knife in the lateral operation of lithotomy, in order to lay bare the groove in the staff. In this incision the transversalis muscle and artery of the perinseum must be divided. Next dissect off 202 DUBLIN DISSECTOR. the erector penis from the crus penis, also the accelera- tores urinse muscles from the bulb and corpus spongiosum urethrae ; detach the transverse muscle from its attach- ments, and remove the vessels and cellular membrane out of the triangular space just now described ; then press the bulb of the urethra to one side, from the crus penis, and between these two bodies we may observe a strong liga- mentous substance, the fibres passing in different direc- tions ; this is the triangular ligament of the urethra or the inter-osseous ligament of the perineum. The apex of this lig- ament is above, and is weak and cellular, being lost in front of the symphysis pubis, on the dorsal vessels of the penis ; the sides are connected to the rami of the pubis and ischium ; its base is directed towards the rectum, being connected in the middle line to the central point of the perinseum, on each side of which it is thin and weak, and gradually lost on the surface of the levator ani. Through this ligament the urethra passes about an inch below the inferior edge of the symphysis pubis, and as this canal passes through it, the ligament sends a lamina on it in each direction, one anteriorly on the bulb, the other posteriorly on the membranous portion of the urethra and prostate gland ; the former is called the anterior, the latter the pos- terior layer of the triangular ligament, and they are separated from each other by Cowper's glands and the artery of the bulb. The anterior layer of the triangular ligament is expand- ed on the bulb, and gives to it the peculiar glistening ap- pearance it now presents ; it also retains it in its situation, and prevents it being detached, as will appear if you en- deavour to draw it out of its place. The posterior layer is continued backwards around the membranous part of the urethra to the prostate gland, the capsule for which it forms, and then becomes continuous superiorly and later- ally with the reflections of the pelvic fascia on the neck of the bladder. Divide a few fibres of the anterior layer of this ligament, and by a little dissection you will expose on each side of the bulb a small glandular body, Cowper's or the anti-prostatic glands ; these are two in number, about the size of a small pea, situated at each side of, and behind the bulb, below the membranous part of the urethra, between the layers of the triangular ligament, and closely connect- ed to the artery of the bulb ; they are covered anteriorly by the acceleratores urinee muscles, and by the anterior layer of the triangular ligament ; from each a small deli- cate duct, about an inch in length, passes forwards, and opens obliquely into the lower and lateral part of the ure- thra, at a little distance anterior to the bulb. Dissect away all the cellular membrane at the side of the rectum, be- DUBLIN DISSECTOR. 203 tween it and the tuber ischli; you will thus expose the greater portion of the levator ani muscle ; press the rec- tum to the opposite side, and you will then observe how this muscle, posteriorly, and the triangular ligament, an- teriorly, close the inferior opening of the pelvis, and sep- arate this cavity from the perinseum. Divide the triangu- lar ligament on one side from the rami of the pubis and ischium, and draw it over towards the bulb of the urethra, which, together with the rectum, press or fasten with a tenaculum, towards the opposite tuberosity of the ischium. In separating this ligament from the bone, the pudic artery and its terminating branches will be seen ; we thus also expose more fully the levator ani muscle. LEVATOR ANI, flat, thin, and broad, situated at the inferior part of the pelvis, broader above at its origin than below at its insertion ; arises fleshy from the posterior part of the symphysis pubis below the true ligaments of the bladder ; thin and tendinous from the obturator fascia, and from the ilium above the thyroid hole ; thick, tendinous, and fleshy from the inner surface of the ischium, and from its spinous process ; the fibres descend obliquely inwards, by the side of the neck of the bladder and rectum ; the anterior pass- ing more backwards than the others, while the posterior are more transverse or horizontal, inserted, the anterior or pubic fibres into the central point of the perineeum, and into the forepart of the rectum, uniting with the fibres from the opposite side. These anterior fibres descend along the side of the prostate gland and the membranous part of the urethra ; the middle fibres into the side of the rectum, pass- ing internal to the sphincters, and united to the outer sur- face of the longitudinal fibres of the intestine ; the poste- rior fibres into the back part of the rectum, and into a ten- dinous raphe, extending from it to the os*coccygis, in which raphe the muscles from the opposite sides unite, also into the two last bones of the coccyx. Use, to raise the rectum when this intestine has been protruded by the efforts of the abdominal muscles to expel its contents ; it also assists in closing this intestine, it compresses the vesiculae seminales and prostate gland ; the anterior portion supports the peri- nseum by raising the common central point, and may also compress and close, like a sphincter, the membranous por- tion of the urethra ; the levatores ani complete the inferior boundary of the pelvis and abdomen, and are opposed to the diaphragm in respiration, being muscles of expiration. The two levatores ani muscles resemble a funnel, with two openings in it inferiorly : the concavity directed towards the pelvis, the convexity to the perinseum ; through the an- terior aperture the urethra passes, through the posterior the 204 DUBLIN DISSECTOR. rectum. On the perinseal surface of this muscle are placed the muscles, the triangular ligament, and the adipose sub- stance of which we have spoken ; its pelvic surface is co- vered by the peritonaeum and by the pelvic fascia, which cannot be seen in the present dissection, but which shall be noticed presently. At the anterior edge of each levator ani muscle fleshy fibres may be observed to surround the membranous part of the urethra very closely. These fibres, particularly at their insertion, will in general be found so united to the le- vatores ani, that they may be considered as portions of these muscles ; they have, however, been described differ- ently by different anatomists, no doubt in consequence of the different appearance they present in different subjects, and from the different mode in which the dissection has been conducted ; Mr. Wilson describes them as follows : COMPRESSORES URETHRA ; each arises by a tendon from the inside of the symphysis pubis, about one-eighth of an inch above the lower edge of the arch, and at nearly the same distance beneath the anterior ligaments of the blad- der, to which, and to the tendon of the opposite muscle, it is connected by loose cellular membrane ; the tendon is at first round, but becomes flat as it descends, and is parallel to and in contact with its fellow ; it then ends in fleshy fibres, which increase in breadth, and which approaching the upper surface of the membranous portion of the ure- thra, separate from those of the opposite muscle, descend along the side of the membranons portion of the urethra, and folding beneath it, again approach the muscle of the opposite side, and are inserted with it into a narrow tendi- nous line, which becomes lost in the common central point of the perinseum. Use, to compress, contract, close, and elevate the membranous portion of the urethra; these fibres encircle the narrowest part of the urethra, that por- tion which is just behind the bulb, and may, by their con- traction during life, form such an impediment to the pas- sage of an instrument into the bladder, as may lead the surgeon to suspect the presence of a stricture, when in re- ality no alteration of structure exists. The origin of these muscles is occasionally distinguished from the levatores arii, by some small veins which pass from the side of the neck of the bladder to join the trunk of the dorsal veins of the penis, but their insertion is confounded with these muscles in perinaeo behind the bulb.* Let the student next replace the triangular ligament, &c., * Mr. Guthrie states, that they arise from two tendinous lines, one on the upper, the other on the lower surface of the urethra, thence the fleshy fibres pass trans- versely outwards, and are inserted into the upper part of the ramus of the ischium. DUBLIN DISSECTOR. 205 and then re-consider the several parts before him, in refer- ence to the operation of lithotomy : he has already ex- amined the triangular space between the erector penis and accelerator urina3 muscles, into which the knife of the ope- rator is to sink in order to reach the groove in the staff'; this space has been fully opened, and the staif can be plainly felt or seen passing above the bulb through the membranous part of the urethra into the bladder : behind and below the bulb is the rectum ; and close to the rami of the pubis and ischium are the internal pudic vessels : the large artery from the pudic, called the deep transverse ar- tery, or the artery of the bulb, may also be observed pass- ing in the substance of the triangular ligament, about an inch below the symphysis pubis. Hence then, in order to lay bare the staff' without injury to the more important parts which surround it, we should endeavour to open the urethra as near to the base of the triangular ligament as possible, as we shall thus be most likely to avoid the ar- tery of the bulb. Suppose the knife of the operator to be lodged in the groove of the staff', and then to be pushed along it into the bladder, the student will perceive that at that moment the posterior layer of the triangular ligament, the anterior fibres of the levator ani, and the left lateral lobe of the prostate gland, must be divided, and from this view he may also learn that the rectum will be protected from injury if the staff be well raised into the arch of the pubes, its groove turned a little to the left side, and the wrist of the operator depressed, so as to elevate the point of the knife, and thus direct it on into the bladder ; as to withdrawing the knife the student may now learn in what direction this can be done with safety and effect, and what parts require to be divided ; it is to be withdrawn slowly and steadily in a direction backwards and outwards, nearly- parallel to the line of the cutaneous incision, the edge so lateralized as to avoid cutting the rectum posteriorly, or the pudic artery externally ; in this part of the operation the middle fibres of the levator ani must be divided, also the adipose substance on its perinasal surface. The student may now withdraw the staff from the bladder, and pass it again and again along the urethra into that cavity ; he will soon perceive how apt the point of the instrument is to de- scend into the sinus of the bulb, and the necessity of de- pressing the handle of the staff, in order to raise the point into the membranous part of the urethra. [This is owing to the fact, that the membranous portion of the urethra does not terminate at the end and bottom of the bulb, but some lines above and before this, hence when the point of the staff is lodged in the bulb, it should be withdrawn a few lines, to disentangle 18 '206 DUBLIN DISSECTOR. it from any fold of the mucous membrane, and then by depressing the handle of the instrument, the point will be raised up to the open- ing through the triangular ligament.] At the same time he should observe, that the latter is about an inch below the arch of the pubes, and that, there- fore, the point of the instrument is not to be too much ele- vated, otherwise it may lacerate the upper part of the ure- thra, and injure some large veins that may be found in this situation. The student may now also examine what occu- pies the space between the urethra and the pubes ; imme- diately above that canal is the upper portion of. the trian- gular ligament, attached to the crura penis ; behind and above this are one or two large veins from the dorsum of the penis, these enter the pelvis along the upper surface of the prostate gland ; above these is a smooth dense liga- ment, the pubic ligament, which is attached to the lower edge of the symphysis pubis, and rounds off the angle between the opposite rami. Posterior to the levator ani, and overlapped by the glu- tceus maximus, is the following small muscle : COCCYGEUS, triangular, at the inferior and posterior part of the pelvis, behind and above the levator ani, arises nar- row from the inner surface of the spine of theischium, the fibres expand along the inner or lesser sacro-sciatic liga- ment, and are inserted, fleshy and tendinous, into the extre- mity of the sacrum and side of the coccyx: Use, to sup- port the os coccygis and to assist in closing the inferior and posterior part of the pelvis ; this muscle is between the le- vator ani and the glutrcus maximus ; it is more distinctly seen within the pelvis. Next let the student divide the central point of the peri- nseum, separate the rectum from the bulb, and draw the former a little downwards from the bladder and prostate gland : he will thus expose the inferior or posterior surface of the neck of the bladder, the flat posterior surface of the prostate gland, also the vesiculic seminales, the termina- tions of the vasa deferentia, and the commencement of the urethra, but the most important part to direct the attention to, is a small triangular space or portion of the bladder, just above and behind the prostate gland, which is bounded on either side by the vasa deferentia and vesiculse semi- nales, posteriorly by the cul de sac of the peritonaeum, and anteriorly by the prostate gland which forms the apex of this triangle ; within this space the muscular coat of the bladder is in contact with the rectum, and from the cavity of the latter the former organ may be perforated during life without injuring any important part; this space is about three inches and a half, or four inches from the anus, DUBLIN DISSECTOR. 207 and is selected by some surgeons as the best situation for tapping the bladder in case of retention of urine, when a catheter cannot be passed through the urethra. The stu- dent may now proceed to examine the pelvic viscera ; for this purpose, separate the left cms penis from the bone, also the left border of the triangular ligament, (if not al- ready done,) and detach the levator ani muscle of the left side from the bone ; with the hand separate the cellular and aponeurotic bands which lie superior to this muscle ; then divide the symphysis pubis, or saw the left os pubis about half an inch external to the symaphysis, divide the left ilio-sacral articulation, cut through the psoas muscle and iliac vessels, and then remove the os innominatum and lower extremity of the left side ; the pelvic viscera will re- main in the concavity of the sacrum and of the opposite os innominatum. These viscera will be rendered more dis- tinct by a little dissection, first, moderately inflating the bladder through the ureter, a ligature having been tied around the penis, the rectum also may be moderately dis- tended with curled hair or a sponge, and attached to the spine by a ligature. The pelvic portion of the peritonaeum should be first attend- ed to ; this membrane may be now seen to descend along the sides and fore part of the rectum to within about three or four inches of the anus, whence it is reflected on the lower and back part of the bladder : the line of this reflec- tion is, in the recumbent position of the subject, opposite 1 the lower margin of the third piece of the sacrum; in the erect posture it will be found on a level with the junction of the sacrum and coccyx ; the peritonaeum is reflected on the bladder between the middle of the vesicular seminales, it then ascends on the back part and sides of this organ to its superior fundus, whence it is continued to the abdomi- nal muscles ; below the line of its reflection on the blad- der, or below the cul de sac, we may again take notice of the triangular space on the inferior fundus of the bladder, before alluded to, as the situation in which that viscus can be punctured from the rectum, in case of retention of urine. The reflections of the peritonaeum from each side of the rectum to the back part of the bladder, are called the pos- terior ligaments and the folds which this membrane forms, one on each side between the bladder and the iliac fossa, are named the lateral ligaments of the bladder ; these shall be more particularly noticed presently. Remark the curved course of the rectum, its dilatation near the anus, also the connexion of the peritonaeum to its upper and middle thirds, and observe that the lower third of this intestine is 208 DUBLIN DISSECTOR. completely below and unattached to this membrane. Next study the connexions of the unirary bladder. Vescica Urinaria, when contracted, is situated in the ante- rior and inferior part of the pelvis behind and below the pubes ; when distended it occupies more or less of the hy- pogastric region ; when contracted, it appears of a flatten- ed triangular form, the base towards the rectum, the apex behind the lower edge of the syrnphysis pubis ; when dis- tended, it presents an oval figure, the larger end towards the rectum, the smaller and anterior end towards the recti abdominis muscles, between the pubes and the peritonaeum ; the axis of the bladder is a line directed through its cavity from one extremity to the other ; the posterior end of this line, if prolonged would touch the extremity of the coccyx, and if continued anteriorly it would reach the linea alba, midway between the pubes and the umbilicus. In the very young subject, the bladder is of a pyriform figure, and is principally lodged in the hypogastdc region. [The form and situation of the bladder vary very much, according to age, sex, and distention. In the foetus arid infant the bladder is nearly cylindrical in form, and almost entirely in the cavity of the abdomen, the cavity of the pelvis proper at that time, being so small, as not to contain it, particularly after the secretion of urine com- mences. In the adult male the form of the organ is ovoidal, the, longest diameter being vertical to the plane of the superior strait of the pelvis. In the adult female, who has borne children, the bladder is more spheroidal in form, is more capacious than in the male, and its longest diameter is transverse. This difference appears to be ow- ing to the pressure exerted upon the bladder, by the gravid uterus. We find also, that the position of the bladder is changed during utero- gestation, particularly in the advanced stage, when this organ, is somewhat raised and projected forward over the pubis, and the urethra is drawn up behind, and nearly parallel to the symphisis pubis. On this account, if necessary to draw off the urine, the point of the catheter being introduced into the orifice of the urethra, the handle must be depressed between the thighs, nearly to the fissure of the nates. If the bladder of the adult be but partially distended with urine, it will remain within the cavity of the pelvis proper, but when fully distended, the superior fundus, rises up above the brim of the pelvis, into the abdomen,, and in some cases, of over distention, it has ascended above the umbilicus. The capacity of the bladder, in the adult will average about one pint, but there is a great difference in individuals in this respect, the capacity being greater in those who are in the habit of retaining their urine for a length of time, than in others, and this is thought by Cruveilhier, to be one cause of the greater capacity in the female ; they, from the habits of society, be- ing more often obliged to retain the urine, for a long time. Again the capacity of the bladder varies with certain morbid conditions, the organ in some cases, being so contracted as scarcely to contain an ounce of fluid, while in others, it is so dilated as to hold several pints. DISSECTOR. 209 According to the anatomist above named, the bladder is proportion- ably larger, before than after birth.] The bladder is connected to the parietes and to the visce- ra of the pelvis by folds of the peritonaeum, and by the re- flections of the pelvic fascia. The folds of the peritonaeum are termed false ligaments, and are five in number, viz. two posterior, two lateral, and one superior : the true ligaments are reflections of the pelvic fascia, and are four in number, two anterior and two lateral. We shall first consider the false ligaments, or the folds of the peritonaeum, which serve to connect the bladder to the pelvic viscera. The posterior ligaments of the bladder are two in number, one on each' side ; they lead from the fore part of the rectum to the back part of the bladder ; each is of a semilunar form, its concavity looking forwards and upwards ; in this fold are contained the ureter posteriorly, and the obliterated hypo- gastric artery anteriorly ; between the posterior ligaments the cul de sac of the peritonaeum descends. This mem- brane will be also found thrown into one or two semilunar folds on the posterior surface of the bladder, provided this viscus be in a state of contraction ; these disappear, how- ever, when it becomes distended : hence it may be inferred, that these folds are designed to admit of the more easy dis- tention of this organ. The lateral ligaments extend, one on each side, from the lateral regions of the bladder to the iliac fossae ; each contains in its duplicature the vas defe- rens in the male subject, and the ligamentum teres of the uterus in the female. The superior ligament extends from the summit of the bladder to the recti muscles ; this portion of the peritonaeum is partially reflected over the remains of the urachus and of the hypogastric vessels. Detach the peritonaeum from the right iliac fossa, and gently draw the bladder and rectum from the pelvis, we shall then observe that the neck and sides of the former are retained in their situation by the reflection of a strong fascia (the pelvic fascia) from the parietes of the pelvis upon this viscus ; these reflections are the true ligaments of the bladder. The pelvic fascia may be considered as a continuation of the iliac fascia ; it descends from behind the iliac vessels and from the brim of the pelvis, to which it adheres, and lines the parietes of the cavity as low down as the upper edge, or the origin of the levator ani muscle ; here the pelvic fascia divides into two laminaB, between which this muscle is en- closed : the external lamina is named the obturator fascia, [or deep perineal fascia] the internal the vesical fascia. The obturator fascia descends between the obturator inter- nus and levator ani muscles, adhering very closely to the former, and sends off the ischio-rectal layer of fascia which 18* 210 DUBLIN DISSECTOR. covers the perinosal aspect of the levator ani muscle ; the obturator fascia is then inserted inferiorly into the great sciatic ligament, into the tuber ischii, and into the rami of the ischium and pubis, where it is continuous with the trian- gular ligament of the urethra, which ligament thus appears to be the continuation of the obturator fascia, from one side of the pelvis to the other. The vesical fascia covers and adheres to the internal surface of the levator ani, lying between it and the peritonaeum ; this fascia descends ante- riorly to the lower edge of the symphysis pubis, and late- rally to a level with a line carried from this point round to the spine of the ischium ; from the pubes it is reflected on the upper surface of the prostate gland, and on the neck of the bladder, forming the anterior true ligaments of this organ; laterally it is reflected from the pelvis on the side of the prostate, and on the lower part of the side of the bladder, just above the outer edge of each vesicula seminalis, and thus it forms the true lateral ligaments of the bladder; posteriorly the vesical fascia becomes thin and cellular, is attached to the side of the rectum, and lost on the nerves and vessels passing into and out of the pel- vis. The vesical fascia thus forms a pouch on each side of the bladder, which assists in closing the pelvis ; it also fixes the pelvic viscera, supports the peritonaeum, and re- sists the pressure of the abdominal muscles and diaphragm. This fascia is perforated by several blood-vessels. The -anterior ligaments of the bladder are two in number ; they arise, each, from the lower margin of the pubis by the side of the symphysis ; pass backwards and upwards on the upper surface of the prostate gland, and expand on the anterior part of the bladder ; many of their fibres may be seen to become continuous with the muscular fibres of the bladder, their inferior or convex surface is united to the posterior layer of the triangular ligament. A depres- sion exists between these two ligaments, along which the dorsal reins of the penis pass from beneath the arch of the pubes to the side of the bladder in their course to the inter- nal iliac veins, in which they terminate ; the pelvic fascia, however, is not deficient between these ligaments, but is con- tinued from one to the other, so as to line this depression and cover the superior surface of these veins. The true lateral ligaments of the bladder are, one on each side ; each is continuous with the anterior ligament, and is formed by the reflection of the pelvic fascia from the inner surface of the levator ani to the side of the prostate gland and of the bladder. The superior and anterior extremity of the bladder is sometimes named the superior fundus; the posterior ex DUBLIN DISSECTOR. 211 tremity, which presses against the rectum, the inferior fun- dus; the intervening portion is called the body, and that part which is connected to the pubes the cervix ; the latter is surrounded by the prostate gland, very little, however, of this gland being above it, a little dissection can separate the base of this gland from this part of the bladder, which it overlaps, the cervix is thus made more distinct, and it then presents somewhat a conical figure; in the adult it lies nearly horizontal, below and behind the pubes ; in the child it is more vertical. If the bladder be moderately dis- tended it will be found to present six regions, on each of which some important object may be noticed. 1st, The superior region, is in contact posteriorly with the convolu- tions of the small intestines, and anteriorly with the recti abdorninis muscles^ to it are attached the urachus and ob- literated umbilical arteries ; posterior to these this region is covered by peritonaeum, whereas anterior to them this membrane is deficient. If the bladder be much distended, this region is sometimes found to incline to the left side. 2nd, and 3rd ; The lateral regions, are contiguous to the sides of the pelvis, to the vesical fascia, and to the levatores ani muscles ; descending obliquely backwards along this region on each side, we find the vas deferens crossing over the obliterated umbilical artery above, and over the ureter below, thus passing internal to both, or nearer to the me- sial line ; the peritonaeum adheres to so much of each late- ral region of the bladder as lies posterior to the vas defe- rens while that portion anterior to it is deficient of this serous covering. 4th, The anterior region is behind the recti muscles, the pubes, the pubic ligament, and the triangular ligament of the urethra ; all this region wants the perito- nseal covering ; towards its inferior part we observe the anterior ligaments of the bladder, between them the dorsal veins of the penis, and below them the neck of the bladder surrounded by the prostate gland, 5, The posterior region is contiguous to the rectum in the male, to the uterus in the female, and in either sex occasionally to the convolu- tions of the small intestines ; all this region is covered by peritonaeum. 6th, The inferior region, in the female, lies on the ureters and on the vagina ; in the male, on the vesicu- lae seminales, the intervening cul de sac of peritonseum, the rectum and the prostate gland ; the superior and posterior part of this region is covered by the peritonaeum ; but an- terior to the line of the reflection of this membrane, from the bladder to the rectum, is the triangular portion of this region, in which the peritonseum is deficient, and which has been already attended to, as the situation in which the 212 DUBLIN DISSECTOR. operation of tapping the bladder from the rectum may be performed. The coats of the bladder are four, viz. 1st, the serous, or peritoneal ; 2nd, the muscular ; 3rd, the cellular ; 4th, the mucous ; the serous is but a partial coat, it covers all the posterior surface, the posterior part of the upper and lower fundus ; also the posterior part of each side. All the ante- rior region, the fore part of the sides, and of the upper and lower regions, are therefore uncovered by peritoneum ; when the bladder is distended there is more of this organ in proportion covered by this membrane than in its con- tracted state. The peritonseal covering of the bladder is very dense, it may be easily dissected off the following. 2nd, The muscular coat consists of fibres which are strong- er and redder than the muscular fibres on any of the hol- low viscera ; they take different directions ; those of the superficial layer run chiefly in a longitudinal direction, are connected anteriorly and inferiorly to the anterior liga- ments of the bladder, and superiorly to the urachus, poste- riorly and inferiorly to the base of the prostate gland ; these fibres are stronger on the anterior and posterior sur- faces than on the sides of the bladder : on the latter regions they run obliquely and are fewer in number. The anterior fibres, from having a fixed attachment, are called by some the delrusor urince muscle : the deep fibres mostly take a cir- cular direction, are weak superiorly, but strong near the cervix, where they arc supposed by some to act as a sphinc- ter muscle ; these circular fibres which have received this name, may be more distinctly seen by everting the bladder, and dissecting off the mucous membrane near the orifice of the urethra on each side of the uvula. At the anterior part of the inferior region there is a compact layer of white dense fibrous substance, into which the muscular, particu- larly the longitudinal, fibres of the bladder are inserted, but which itself does not appear to be very muscular ex- cept near the cervix; this structure will be found to cor- respond with a particular region, which will be noticed presently in the interior of the bladder, and which is called the trigone, or the velum. In addition to the longitudinal and circular fibres, a deeper, but only a partial lamina of fibres can be seen having a reticular arrangement. Be- neath the muscular is the 3rd, or the cellular coat ; it invests the whole organ, is very elastic, and seldom contains any adipose substance. Open the bladder by a perpendicular incision through its anterior part ; and the 4th. or the mu- cous coat, will be observed ; this is pale, and thrown into many folds, particularly if the bladder had been empty, foi this membrane has no contractile power; through it the DUBLIN DISSECTOR. 213 muscular fibres project, presenting a reticulated appear- ance, and very frequently the mucous membrane forms pouches, or small sacks, between these : inferiorly is seen the orifice of the urethra ; is is somewhat of a crescentric figure, a very small tubercle (the uvula) projecting into it from below : posterior to this the mucous membrane pre- sents a smooth and dense appearance throughout a small triangular space called the velum or trigone ; at the poste- rior angles of this space the orifice of each ureter may be observed, the line extending between these forms the base of this triangle ; this line is somewhat semilunar, and con- tains strong muscular fibres ; the sides of the trigone are defined by lines drawn from each ureter to the uvula ; each is from an inch to an inch and a half in length ; be- neath the membrane covering each of these lines, pale mus- cular fibres may in general be found; these have been named by Mr. Bell, the muscles of the ureters, who describes each as arising from the vesical extremity of the ureter, and thence descending obliquely forwards and inwards, to be inserted by a tendon common to its fellow into the uvula. The use which he assigns to them is, to restrain the termi- nation of the ureters, and preserve the obliquity of the pas- sage of these tubes through the coats of the bladder while it is being contracted ; for, says he, without this provision, the urine would be sent retrograde into the ureters, instead of forward into the urethra. These lines, however, seldom present this structure so distinctly as has been described, and how far their supposed use is correctly ascribed to them is very questionable. The uvula of the bladder is a small eminence at the apex of the trigone, much better marked in some than in others ; it is merely a thickening and peculiar organization of the sub-mucous tissue ; it is nearly opposite, but a little anterior to the third or middle lobe of the prostate gland. The trigone is the most sensi- ble and vascular part of the bladder ; posterior to the tri- gone the bladder is frequently, particularly in old subjects, dilated into a sort of pouch. In the female the trigone is smaller, but broader in proportion than in the male, and the uvula is less distinct. [There is one feet in reference to the bladder, as often found on post mortem examination, which should be borne in mind, this is a remarkable contraction of the bladder, from having been empty be- fore death, the cavity being scarcely large enough to hold a couple of ounces of fluid, and the muscular coat appearing very thick and dis- tinct, and the whole organ is almost concealed under the arch of the pubis. This is to be particularly distinguished from the contraction which depends upon a morbid condition, in which case there will be other evidences of disease.] 21 DUBLIN DISSECTOR. The bladder is occasionally found in a diseased state, in- flammation of it (cystitis) may be general or confined to one particular part ; the portio'n which is most frequently so affected is that near the neck, and commonly arises from the presence of a rough stone ; from the naturally pale ap- pearance of the mucous membrane in the dead body, any crowding of vessels containing arterial blood which takes place in inflammation makes this state of parts easy of de- tection ; and this is the case in chronic inflammation or ca- tarrh of the bladder : if the inflammation be violent, the muscular coat may become engaged, and abscesses and ul- cers are not unfrequently the consequence ; they sometimes proceed so far as to destroy a portion of the bladder, and form communications between it and the neighbouring vis- cera ; with the rectum in the male, and vagina in the fe- male ; they have also been known to open into the cavity of the abdomen, producing peritonitis and death from ex- travasation of urine ; abscesses about the neck of the blad- der are generally found as a consequence of the operation of lithotomy or of fatal retention of urine, or diseased prostate gland. [Inflammation of the bladder is sometimes caused, from the urino being retained too long. Inflammation may terminate in resolution suppuration, or gangrene, which last is very rare. We sometimes find a softening of the mucous membrane, sometimes also hypertro- phy of the tunics, but more particularly of the muscular coat, and this generally arises from some obstruction about the neck of the bladder or in the urethra, which prevents the ready discharge of the urine.] Calculi are not uncommonly formed in the bladder : their formation is confined to no particular period of life ; they are found in very young children and in persons of middle and advanced age ; they are very seldom met with in females, as the size of the urethra in that sex allows them to be discharged before they become large, probably also the tendency to their formation is not so strong in females. The stones which are found in the bladder are either origi- nally formed in the kidneys, and pass through the ureters into the bladder, or they are at first formed in the bladder itself. Calculi lie either loosely in the cavity of the blad- der, or are confined to some fixed situation from particular circumstances ; when they are of a small size, they are sometimes lodged in pouches, formed by the protrusion of the mucous coat of the bladder, between the fasciculi of its muscular fibres. Urinary calculi have sometimes a smooth, uniform surface, but more frequently the surface is granulated and rough. The urethra is the next division of the urinary organs to DUBLIN DISSECTOR. 215 be examined ; as this canal, however, in the male, is the common passage for the urine and seminal fluid, or as it is a part both of the urinary and generative organs, we shall postpone the description of it until we have considered the latter. DISSECTION OF THE ORGANS OF GENERATION IN THE MALE. The organs of generation in the male are the testicles and their appendices, the vesicular seminales ; the prostate and anti-prostatic glands, (the latter have been already ex- amined ;) the penis, and the urethra. We shall describe these organs in the following order : 1st, the testes, with their coverings ; 2nd, the vasa deferentia ; 3rd, the vesicula? seminales ; 4th, the prostate gland ; 5th, the penis, and 6th, the urethra. 1st. THE Tesl.es ; these two glands ore, in the very young foetus, contained in the abdomen beneath each kidney ; a short time, however, previous to birth, they descend into that situation which they are found to occupy in the adult, and are surrounded by several tunics, viz. the scrotum, dar- tos, superficial fascia, tunica communis, tunica vaginalis, and tunica albuginea. The Scrotum is a process of common integument con- tinued from the inner side of each thigh, and from the pe- rinseum and penis ; it is generally of a dark brown colour, thinly covered with hair, and very rugged, being thrown into numerous rugre, it is so thin that the small sub-cuta- neous veins and sebaceous follicles can be seen through it, these latter secrete the peculiar perspirable matter of this region, the prominent hard ridge or raphe is continued from the perina3iim along its middle line as far as the penis. The Dartos is the cellular tissue immediately subjacent to the skin, it usually presents a. reddish appearance, a num- ber of small vessels being distributed through it ; its tex- ture is very loose, and is readily distended in emphysema or in anasarca ; it never contains any fat ; it is somewhat more dense in the mesial line than at either side. The dartos is connected to the rami of the pubis and ischium of each side, and to the raphe in the middle, thence it as- cends a short way between the testes to the urethra, and thus assists the superficial fascia in forming the septum scroll. The dartos manifests during life a degree of con- tractility above that which the cellular tissue enjoys in any other situation ; it has therefore been considered by some as a cutaneous muscle ; this idea is most probably incor- rect, although it certainly possesses the power of corruga- ting the skin, distinct from that rolling motion of the tes- ticle produced by the cremaster muscle; posteriorly the 216 DUBLIN DISSECTOR. dartos frequently appears to derive a few muscular fibres from the sphincter ani. [Meckel suggested, that the Dartos was the transition between muscle and cellular tissue. Cruveilhier looks upon it, as being the same tissue with the external coat of the vagina, with the external coat of the veins, and the substance of the nipple. By some anato- mists the Dartos has been considered an expansion of the guberna- culum testis, and not to exist in the scrotum, until after the descent of the testicle ; but on the other hand it has been found in the scrotum of the fetus, before the descent of the testicle, and in the case of an adult, in whom the testicle had not passed down through the ring, Cruveilhier satisfied himself of the co-existence of the gubernaculum and the dartos, independently of each other.] Beneath the dartos is the superficial fascia of the scrotum, this is continued from that of the abdomen around each spermatic cord, testicle, and epididymis ; it is thin, loose and reticular, and becomes continuous with the fascia of the perinaeum : as this fascia envelopes the cord and testis on each side, it, assisted by the dartos, forms the septum scroll, and so retains each testicle at its own side. The tu- nica communis is composed of the expanded fibres of the crernaster muscle and of fine connecting cellular mem- brane ; this tunic surrounds the cord and testis : the fibres of the cremaster are expanded chiefly on the forepart and sides of the testis. The tunica vaginalis was originally, that is, in foetal life, a process of the peritonaeum, having been prolonged along the cord and around the testicle as the lat- ter was descending from the abdomen to the scrotum ; at this early age, the tunica vaginalis in the scrotum commu- nicated with the general cavity of the peritonaeum by a sort of canal which led along the forepart of the cord from the abdomen to the scrotum : this canal, however, about the period of birth was closed by the adhesive process, and ever afterwards the cavity of the tunica vaginalis is quite distinct from that of the peritonaeum.* The tunica vagi- nalis, therefore, is a serous membrane, a shut sac, suspend- ing, and partly enclosing the testicle, and also reflected over its anterior part and sides : that portion of it which suspends the gland, and which lines the scrotum, may be named the tunica vaginalis scroti ; while the reflected por- tion which covers the sides and forepart of the testicle is the tunica vaginalis testis. This membrane is so loosely connected to the scrotum that it can be detached from it with little force ; it is thence reflected on the sides and fore- part of the epididymis and testis, it also ascends a short * When this canal is not thus closed, a hernia usually occurs, which is named " congenital inguinal hernia." DUBLIN DISSECTOR. 217 distance on the forepart of the cord ; the posterior part of the epididymis is altogether uncovered by it : as it is con- tinued from the epididymis to the testicle it passes in be- tween these organs, particularly on their outer side, so as to form a sort of pouch between them. Both the testicle and epididymis are in reality behind this serous mem- brane, and nothing is contained within its cavity except the serous fluid, which lubricates its opposed surfaces, and which facilitates that gliding motion which the testicle un- dergoes in the scrotum. [The cavity of the tunica vaginalis will receive from one to two ounces of fluid without distention, but when distended, as in hydrocele, it sometimes contains even quarts.] When the anterior part of the tunica vaginalis is divided, we see its internal surface smooth and polished, and shin- ing through its reflected layer which covers the testis, we can discern the next tunic of this gland, tunica albuginea : this is a dense fibrous membrane ; it forms the proper cap- sule of the gland, adheres to it, preserves its peculiar form, and sends several processes or septa into the testicle, which will be seen when the body of the latter shall have been opened ; it has no connexion to the epididymis : it is dim- cult to dissect otf the reflected layer of the serous mem- brane, or the tunica vaginalis testis from the tunica albu- ginea, they are so intimately united ; through the latter several blood vessels can be distinctly seen ; indeed the al- buginea can easily be separated into two lamina?, the ex- ternal strong and "fibrous, the internal soft and vascular, formed by the ramifications of the spermatic artery. Each testicle is of an oval form, flattened on each side, also a little on the back part beneath the epididymis ; it is suspended rather obliquely, the superior extremity being directed for- wards and outwards, the inferior backwards and inwards. [The testicles are not suspended at the same level, that of the left being lower down than that of the right side, for two reasons, says S r A. Cooper, the one to allow of the disposition of the p?n ; s to one side of the median line, the other to ailow of tho ore testicle gliding upon and above the other, in the close adduction and crossing of the thighs. It is said that there is usually a difference in the size of the testicles, but if any, it must be but slight as some anatomists jjive the difference in favor of the left, and others in favor of the right. In some cases as stated there is but one testicle, while in others there are more than two. Those cases reported as belonging to the former class, are almost always cases, in which one of the testicles has not descended into the scrotum. Cruveilhier however dissected a subject in which he found but one testicle. It does not appear to be satis, faclorily proved, that there are ever more than two of the organs ; the apparent instances, have been in consequence of the presence of 218 DUBLIN DISSECTOR. tumours of some kind. I have seen two of these cases, in which the individuals supposed that they had three testicles, but on examination, the third body proved to be morbid, in one case it was a small hyda- tid. The situation of the testicles, in foetal life, is verv different from that in which they are usually found after birth. At the middle of the third month of utero- gestation, the cavity of the abdomen, com. municates on either side, with the cavities of the scrotum or sacculi testium, by short oblique canals, which at this period correspond to what in the subsequent development of the parts, constitute the ab- dominal rings and inguinal canal. At this period the peritonaeum lining the abdomen, is continued down into the sacculi,forming small pouches. The testicle itself is in the cavity of the abdomen, on the psoas muscle below the inferior extremity of the kidney ; and is poste- rior to the peritonaeum like all the abdominal viscera, that membrane however, is reflected over the sides, and fore part of the testis, from the lower end of which proceeds a small ligament, the gubernaculum testis which terminates at the upper and inner part of the scrotum, being also behind the peritonaeum. At this time the spermatic vessels are quite short, and descend a little obliquely to the posterior border of the testicle, while the vas deferens passes obliquely over the iliac vessels, into the pelvis. This original position of the testis and its subsequent descent, explain the remarkable length of the spermatic vessels in the adult. Being thus placed the testicle gradually descends towards the scrotum, as is said by some, from the contraction of the guberna- culum, until usually in the course of the seventh or eighth month, of utero-gestation it is lodged in the sacculus testis; having fairly reached this cavity the passage from the abdomen contracts and becomes completely obliterated, so that there is no longer any communication between the several cavities, and the serous membrane of the pas- sage is converted into cellular tissue, which is sometimes the seat of hydrocele of the cord. The closure of the passage after the descent of the testicle, does not always take place, and then a portion of in- testine may descend with the testicle, constituting congenital hernia, or fluid may pass down into the sacculus, which is called congenital hydrocele. The testicle while in the cavity of the abdomen has a proper and complete fibrous covering, the tunica albuginea ; after it gets into the sacculus, the peritonaeum which invested it in the abdo- men, becomes the tunica vaginahs testis, while the original serous lining of the scrotum, is the tunica vaginalis scroti, and the two to- gether, constitute the tunica vaginalis communis, exterior and pos- terior to the cavity of which is the testicle, and within which cavity, true hydrocele and hematocele take place. Both testicles do not always descend, one is sometimes retained in the abdomen or be- comes entangled in the passage, and may in after life be confounded with concealed inguinal hernia. Weight and Measurements of the Testicle. These differ much in different individuals ; on the average they are from twenty-two to twenty-four lines in length, from twelve to eighteen lines broad, and from seven to eight lines thick. Their average weight is about six drachms, the epididyrnis ranging from two to three scruples ; Sir A. Cooper gives the weight of the testicle as high as one ounce. The DUBLIN DISSECTOR. 219 color of the organ is a greyish white depending upon the color of its tunics.] Bent like an arch, along the posterior surface of each testicle, is the epididymis, long and narrow, large above, (globus major,) narrow in the middle, (body,) and again enlarged below, (globus minor,) attached to the testicle above by vessels, and in the rest of its extent by the re- flected layer of the tunica vaginalis, closely on the inter- nal, but very loosely on the external or femoral side ; from its inferior extremity the vas deferens proceeds, and thence ascends along its internal side. Divide the tunica albugi- nea anteriorly, and we observe the testicle to be composed of a soft greyish or yellowish pulpy substance, which, when opened out a little, and floated in water, is found to consist of numerous fine tortuous shreds or vessels of deli- cate texture, loosely connected to each other ; some are of considerable length, and with a little care may be drawn out of the gland to the extent of two or three feet ; they are placed in packets or fasciculi, which are separated from each other by fibrous bands or septa, which are de- rived from the tunica albuginea, and which may now be seen to pass in considerable numbers through the gland towards the back part, where they join the corpus Highmor- ianum; this name is applied to a long fold or process of the tunica albuginea, which projects into the back part of the gland ; it consists of two laminae, between which the vessels and nerves of the testicle are enclosed ; this pro- cess is broader above than below, is perforated in the for- mer situation by the excretory ducts of the testicle ; to its anterior border and sides are attached the sepimenta or processes of the tunica albuginea before mentioned. This process is also more properly denominated the "medias- tinum testis" as it plainly consists of two laminae, and con- tains in the interspace the excretory portion of the gland. From the several collections of small tubes, which are dis- posed between these bands or septa, about twelve or twenty larger vessels may be seen to proceed in parallel lines to- wards the back part of the gland ; these are the tubuli recti ; they enter the mediastinum, and if one lamina of this pro- cess be raised off they will be seen entangled with each other, and with the vessels and nerves of the gland ; this structure receives the name of Rete Testis, it is placed near the posterior part of the gland, between the lamina? of the mediastinum or the corpus Highmorianum ; from the up- per part of this tissue five or six tortuous vessels ascend obliquely backwards, pierce the tunica albuginea, and ar- rive at the head of the epididymis ; here they increase in size, and become coiled or convoluted ; these are the vasa 220 DUBLIN DISSECTOR. deferentia or coni vasculosi ; they all terminate in the head or globus major of the epididymis, and unite into one small duct (the vas deferens), which is twisted and coiled over and over again in a most extraordinary and peculiar man- ner. The body and globus minor of the epididymis are solely composed of this convoluted vessel, which by care may be unravelled to a great extent : the convolutions of this tube, of which the epididymis thus consists, are con- nected to each other by fine cellular tissue and by the re- flected tunica vaginalis; the epididymis has no fibrous capsule like the testis ; from its lower extremity the vas de- ferens at length escapes, and increasing in size and density, this duct bends upwards along the inner side of the epidi- dymis, and a little above the head of the latter it becomes connected to the spermatic vessels and cremaster muscle ; with these it continues its course obliquely upwards and outwards along the inguinal channel, and through the in- ternal abdominal ring : it here separates from the sper- matic vessels, the latter ascending towards the spine, while the vas deferens passes backwards, inwards, and down- wards, enclosed in the lateral fold of peritonaeum, which conducts it to the bladder, along the side and inferior fun- dus of which it runs internal to the vesicuia seminalis, and converging to its fellow : at the base of the prostate gland each vas deferens joins the duct of the corresponding vesi- cula, and the union of these forms the ductus ejaculatorius communis which runs through the prostate obliquely for- wards and inwards, and opens into the prostatic portion of the urethra on the side of the verumontanum, [anteriorly, being from eight to ten lines in length.] While the vas deferens is contained in the spermatic cord, it lies posterior to the spermatic arteries and veins, and to the cremaster muscle; as it passes through the internal ring it hooks round the outer side of the epigastric artery, being separa- ted from it by the spermatic artery alone ; the vas deferens next passes over the psoas and iliac muscles, the external iliac artery and vein; it then bends over the obliterated hypogastric artery and descends internal to it ; and in the same manner it next crosses over the ureter, so as to lie at first anterior to that tube, or between it and the bladder, and then to descend along its internal side ; the vas defe- rens then runs between the bladder and rectum, near to its fellow, and internal to the vesicula seminalis, as far as the prostate gland, which it perforates in the direction before mentioned. This vessel has a peculiar hard wiry feel like whip-cord : its calibre is small ; its coats are two in num- ber, an internal mucous, and an external, very thick, firm, and white like cartilage. Between the vesiculse each vas DUBLIN DISSECTOR. 221 deferens is flattened, enlarged, and often covuluted ; when it enters the prostate it again contracts, and its firm exter- nal tunic ceases. In some a second duct will be found to leave the testis and to run for some distance parallel to the vas deferens, which in some cases it will join, while in others it will be found to end in a cul de sac. The spermatic cord extends from the epididymis to the internal abdominal ring; it consists of the vas deferens, spermatic artery, veins, nerves, and lymphatics ; this fasciculus of vessels is covered by loose cellular membrane, and by the cremaster muscle : beneath the latter the vessels of the cord will be found joined together by a fine but tolerably dense mem- brane, named the tunica vaginalis of the cord; this mem- brane is the remains of that portion of peritonaeum which in the foetus accompanied the spermatic vessels of the scro- tum, and which after birth lost its serous characters, and became converted into condensed cellular membrane ; this covering is strengthened by that prolongation of the fascia transversalis which is continued from the internal abdomi- nal ring along the spermatic vessels. The spermatic artery arises from the abdominal aorta below the renal artery, and not unfrequently from the latter ; it descends along the psoas muscle [over the ureter,] passes through the internal abdominal ring on the outer side of the epigastric artery ; it then enters the spermatic cord, and is conducted to the back part of the testicle ; it divides into several branches which enter the rete testis ; these subdivide minutely as they proceed into the substance of the testicle, in which they terminate in the commencement of the tubuli semini- feri and of the spermatic veins. The last named vessels leave the rete testis, twine around the arteries, and then as- cend in the spermatic cord ; a little above the testicle these vessels become very tortuous, and form a plexus, which is named the Corpus Pampiniforrne : the spermatic veins then accompany the spermatic artery through the inguinal canal and along the psoas muscle towards the spine : the sper- matic vein on the right side generally ends in the inferior cava near the entrance of the right renal vein ; the sper- matic vein on the left side frequently ends in the left renal vein. [The left, spermatic vein, most commonly ends in the left renal vein and this will explain the fact, that varicocele most commonly occurs on the left side. The left spermatic vein terminates in the left renal vein, nearly at a right angle, while the latter terminates in the abdominal vena cava, also at nearly a right angle, hence the re. turn of the blood from the left testicle must necessarily be retarded, having to describe these two angles, while the blood from the right testicle will readily flow into the vena cava into which the right 222 DUBLIN DISSECTOR. spermatic vein empties very obliquely. The spermatic veins in vari- cocele, are sometimes so much distended, as entirely to destroy the usefulness of the valves and then if the cord be divided below the ex- ternal abdominal ring, a direct hemorrhage from the vena cava will ensue. I have seen a cat--e of this kind in a man twenty-seven years of age, who was castrated on account of a varicecele of twenty years standing, in which the hemorrhage from above was profuse, the di- lated veins being nearly as large, as the end of the little ringer. Be- sides the true spermatic artery, there are two other arteries connected with the cord, the deferential, and the cremasteric. The deferential artery, is a branch of the vesicle, one of the branches of the internal iliac, it comes off in the pelvis, and applies itself to the vas deferens, which it follows up over the brirn of the pelvis, and the external iliac vessels; at the out side of the epigastric it passes through the internal ring into the inguinal canal, and thence passes down to the testicle still following the vas deferens. The cremasteric artery is a branch of the epigastric, and is so called, from being distributed principally in connexion with the cremaster muscle. I have found the deferential artery on both sides, quite as large as the spermatic.] The nerves of the testicle are derived chiefly from the spermatic plexus, which is formed by the union of branch- es from the lumbar ganglions of the sympathetic, with fil- aments from the splanchnic nerves and from the renal plexus ; the cremaster muscle is also supplied by branches from the lumbar plexus of spinal nerves, hence this muscle is, to a certain extent, voluntary. The Vesicula seminales are two in number ; they are situ- ated on the inferior surface of the bladder behind and above the prostate gland, on the outer side of the vasa dcferentia, and anterior to the rectum. [These organs are in fact, placed in a kind of fissure formed by the apposrtion of two cylindroidal bodies, the rectum and the bladder, and are imbedded in a mass of dense cellular tissue traversed by veins, so that they are not brought into view until this substance is dissected away. In these veins, I have several times found the phlebolites or vein stones.] Each is of an oval figure. [In length they are from two inches to two and a half, in breadth, half an inch, and in thickness two to four lines; their color is a greyish white depending upon the external tunic, their volume is greater in the middle aged than in the young or old subject, they are sometimes very small, and in some cases one is wanting.] The superior and posterior extremity is round, and in contact with the ureter ; the anterior extremity is narrow, connected to the prostate gland, and ends in a small duct, [a line and a half in length] which joins the vas deferens ; the union of these forming the common seminal or ejacula- tory duct, which latter passes obliquely forwards and in- DUBLIN DISSECTOR. 223 wards through the prostate gland, and opens into the ure- thra by the side of the verumontanum, [Anteriorly, being from eight to ten lines in length, and running parallel with its fellow under the urethra.] Although the vesiculse look like a congeries of cells, yet "by dissection they may be unravelled, so as to appear as one continued tube convoluted or coiled very much, the different coils communicating with each other. [When the vesicles are thus unravelled, their length is from four to eight inches. Cruveilhier has seen one a foot iu length.] These organs are covered by a dense fascia, which is continued from that covering the prostate gland. Each vesicula consists of two tunics, viz. mucous membrane in- ternally, and peculiar grey substance externally, somewhat similar to, but softer than the outer coat of the vas deferens. The vas deferens communicates more freely with the cor- responding vesicula than the latter does with the urethra, hence air or fluid injected into the vas deferens will gener- ally distend the vesicula seminalis of the same side before it escapes into the urethra. These organs are generally believed to contribute some additional secretion to the semi- nal fluid, rather than to serve as reservoirs for the latter ; their exact use, however, is not well known ; they are wanting in many animals. The Prostate gland is situated at the anterior and inferior part of the pelvis, behind the triangular ligament, and in front of the rectum, to which it is connected by cellular membrane; it surrounds the neck of the bladder, and is attached by the anterior ligaments of this organ to the lower edge of the symphysis pubis, from which it is about three-fourths of an inch distant. The prostate gland is somewhat heart-shaped, or triangular ; it is also compared to a chestnut ; the base or larger extremity is posterior, and connected to the vesiculse seminales ; the apex is anterior, and extends to within a short distance of the triangular ligament ; the neck of the bladder, and about an inch of the urethra run through its substance, but a small portion of it lies superior to the neck of the bladder and urethra; this part is convex, and is covered by the dorsal veins of the penis, and by the anterior ligaments of the bladder ; the inferior or posterior surface of the gland is almost flat, a slight groove is generally observable on it, extending along the mesial line ; this surface is attached to the forepart of the rectum, and may be felt distinctly either in the living or in the dead subject by the finger introduced into the in- testine about two inches and a half above the anus; the sides of the gland are smooth and round, and are covered 224 DUBLIN DISSECTOR. by a strong fascia, by several veins, and by the levatores ani muscles. In the base or posterior end is a notch for the entrance of the common ejaculatory ducts ; this notch, together with the groove on the posterior surface, and the passage of the urethra above this, have caused this gland to be described as consisting of two lateral portions, called the right and left lateral lobes ; these are connected to each other posteriorly by a small transverse process, called the middle lobe; this may be seen by detaching the vesiculse seminales, and vasa deferentia from the bladder, and leav- ing them suspended by their common ducts, the middle lobe of the prostate will then be seen to pass from one lateral lobe to the other, and to be closely connected to the mucous membrane of the bladder. [The prostate gland weighs about five drachms, its length is from eighteen to twenty-one lines, its breadth from fifteen to eighteen lines, and its thickness from nine to twelve lines.] It has also a firm resisting feel, is of a greyish colour, and appears to possess a very compact structure; this, however, is chiefly owing to the strong fascia which in- vests it, and which forms its capsule : the capsule has been already described as being partly derived from the poste- rior layer of the triangular ligament, which expands on the sides and inferior surface of the gland, and partly from the reflection of the pelvic fascia from the pubes called the anterior ligaments of the bladder. Next continue the in- cision which was made in the forepart of the bladder, through the upper part of the prostate, so as to lay open the urethra, we shall perceive how this gland surrounds the canal, also the greater thickness of its lateral portions. The prostate gland consists of several follicles or acini closely connected to each other, and covered externally by the capsule, and internally by the mucous membrane ; these follicles open by several small ducts, ten or twelve, on the lower surface of the urethra, on either side of the verumon- tanum ; some small ducts also open on the upper surface of the canal. [This organ is divided in the lateral and bilateral operations for stone, and is easily torn after being once cut into.] The Penis is covered by the common integuments, and by the superficial fascia ; the skin is thin and loose, it is continued from that of the abdomen and scrotum around this organ, and extends some way beyond it in the form of a loose fold, the prepuce; from the extremity of this process the skin is reflected inwards as far as the corona glandis, where ft becomes very thin ; it is thence continued over the glans penis to the orifice of the urethra, where it is DUBLIN DISSECTOR. 225 continuous with the lining membrane of the urethra ; infe- rior to this opening it forms a fold, the fraenum preputii ; the prepuce, therefore, is only a fold of the common inte- gument, the sides of which are connected together by very loose reticular tissue ; this fold is expanded when the pre- puce is drawn back, or when the penis becomes distended ; the inner side of the prepuce is of more delicate texture than the external, and that portion of it which is continued over the glans is still more delicate than either. Beneath the skin, around the corona glandis, are a number of small sebaceous glands, glanduloe odorifene, or Tysoni, [Which secrete a white oleaginous substance the smegma preputii, which accumulates from want of cleanliness and becoming acrid, causes excoriations, which may be mistaken for syphilitic sores. The prepuce is sometimes too short and instead of covering the glans penis is contracted around the neck of the organ behind the corona glandis, this is called paraphymosis ; on the other hand it sometimes covers the glans but cannot be drawn back so as to ex- pose it, and this is phimosis, for which circumcision is performed. It is said that those who have the prepuce long are more apt to con- tract the venereal disease than those in whom it is shorter.] The superficial fascia which covers the penis is continued from that of the abdomen, and extends around the penis as far as the corona glandis ; it is thick and strong posteriorly, where it is reflected from the linea alba on the penis, so as to form the superficial suspensory ligament of the latter ; anteriorly it is loose and delicate. Beneath these coverings the penis is found to consist of two long cylindrical bodies, termed the crura or corpora cavernosa penis ; each of these is composed of a strong, elastic, tendinous and fibrous sub- stance [which is called the theca,] forming a sort of tube, which is filled with a soft cellular or erectile tissue, through which a large artery, and many small tortuous veins, run from one end to the other. Each crus penis commences narrow in front of the tuber ischii, and adheres to the rami of the ischium and pubis, as far forwards as the symphy- sis ; anterior to this the crura become inseparably united, and continue so as far as the corona glandis; here each crus ends in an obtuse point, over which the glans penis, which is the expanded extremity of the corpus spongiosum urethrse, is folded ; the two crura are attached to the sym- physis pubis by the true suspensory ligament, which is very strong, and of a triangular figure ; it arises from the sym- physis, and is inserted into each crus ; it consists of two laminae, between which the dorsal vessels and nerves of the penis pass. The crura penis are separated from each other by an imperfect tendinous septum, composed of parallel 226 DUBLIN DISSECTOR. fibres, with such intervals between them that the cavity of one crus communicates with, and can be injected from that of the other ; this septum is named pectiniforme* The cru- ra penis are somewhat conical, the apex of each being at- tached to the ischium and pubis, the base supporting the glans; they are round externally, flattened towards each other ; a wide and deep groove exists between them infe- riorly, which contains the urethra, and a more superficial one superiorly, in which the dorsal vessels and nerves of the penis run. The erection of the penis during life is caused by a greater quantity of blood than usually circu- lates through this organ being propelled by an increased action of the arteries into the small vessels of the corpora cavornosa penis, this increased action being induced by a peculiar excitement of the nervous energy : anatomists are not agreed as to the exact structure of the corpora caver- nosa, or as to the proximate cause of their erection during life, or how the blood is circumstanced during that condi- tion ; some consider that the arteries pour their blood into the cells of the cellular tissue which surrounds them, so as to cause their distention, and that from these the blood is slowly and gradually absorbed by the veins ; others con- ceive that the arteries directly communicate with the veins, and that these latter vessels are tortuous and coiled to such a degree as to form plexuses which serve to retard the course and delay the return of the blood, and so cause the disten- tion and consequent erection of the whole organ.* The Urethra extends from the neck of the bladder to the extremity of the penis [and averages about eight inches in length, its diameter varying at different points ;] it is lined by a fine mucous membrane, which is continuous posteri- orly with the mucous membrane of the bladder, and ante- riorly with the thin integument, which is reflected from the inside of the prepuce, over the glans penis, as far as, and even within, the orifice of the urethra. Tnis membrane is covered at first by the prostate gland, and this portion of * In a paper in the Dublin Hospital Reports, vol. v., Dr Houston ascribes the erection of the penis, in a great degree, to the mechanical obstruction of the blood in the vena magna dorsalis penis, caused by the action of a pair of muscles, named the " compressors venae dorsalis penis ;" these muscles are very distinct in the dog and in other animals, and Dr. H. describes analogous fibres in the human subject; he states that they arise from the rami of the pubis, above the origin of the erectores penis and of the crura, thence the fibres ascend forwards, forming on each side a thin, fleshy, and tendinous stratum, which is inserted in common in the mesial line above the vena dorsalis; these may, perhaps, be regarded as portions of the erectores penis which instead of being inserted into the crura mount over them, in order to compress the vena dorsalis. The developenient of these fibres, however, in man appears so irregular, weak, and imperfect, that I cannot concur in ascribing so much influence as appears to be justly attributed, by com- parative anatomists, to this more perfect structure in some of the lower animals. DUBLIN DISSECTOR. 227 tne canal is called the prostatic portion of the urethra ; the next succeeding portion is covered by the compressores urethrse muscles, by the triangular ligament, and by a pe- culiar reddish or spongy-looking cellular tissue, which con- tains several small blood-vessels, chiefly veins ; this part of the urethra is called the membranous portion ; the remainder of the canal is covered by a cellular and vascular sub- stance of a dark red or purple colour, named the corpus spongiosum urethrse, which commences in the bulb, and ends in the glans penis ; this portion of the urethra is named the spongy portion. The first, or the prostatic por- tion of the urethra is within the pelvis ; it is about an inch and a quarter, or an inch and a half in length ; in the erect position of the body its direction is downwards and for- wards ; it is nearer to the upper than to the lower surface of the gland. [The membranous portion is from six to ten lines long. Cruveil- hier states that it differs in length at its two edges, being superiorly an inch in length, and inferiorly but six lines, owing to the projection backwards of the bulb. This portion of the urethra, is the more common seat of stricture, which sometimes leads to the formation of fistula in perineo. There may be a temporary obstruction here to the passage of the catheter, from a spasmodic contraction of the com- pressor urethrae muscle, which is to be overcome, by gentle but steady pressure. The same thing may occur in that part of the urethrse covered by the accelerator urinae muscle.] It is described in general as being concave towards the pubes : it is, however, but very slightly so, it runs nearly horizontal, about three quarters of an inch below the sym- physis pubes. The spongy portion commences in the bulb in front of the triangular ligament, extends to the extremity of the canal, and ends in the glans penis. [Its length will depend upon that of the penis, but allowing two to two and a quarter inches for the prostatic and membranous portions, this part will average from five and three quarters to six inches.] This part of the canal is surrounded by a vascular and cellular texture, named the corpus spongiosum urethrse, which has some resemblance to the corpora cavernosa penis. The corpus spongiosum urethrse consists of a num- ber of fine cells, which communicate with each other ; through these an artery from each side (a branch from the internal pudic) extends; these vessels send oif numerous branches, which pour their blood into the surrounding cells, from which the veins afterwards absorb it ; the bulb and the glans penis are expansions of this cellular texture, the former on the inferior, the latter on the superior part and sides. This spongy substance is invested by a fine, but strong 228 DUBLIN DISSECTOR. and semi-transparent aponeurosis, very different from that which covers the corpora cavernosa. The corpus spongio- sum surrounds the urethra, but is thicker interiorly and laterally than superiorly ; there is no direct communica- tion between the corpus spongiosum urethra) and the cor- pora cavernosa penis, the one can, therefore, be distended with air or injection without the other, or both may be in- jected with different coloured fluids. In order to inject the crura penis, make a small opening in each crus near its attachment to the ischium, insert a pipe into one of these, and force warm water through it ; this will soon escape through the opening in the opposite crus, carrying along with it the blood which was contained in the cells, then se- cure with a ligature the opposite crus, and inject some co- loured fluid. To prepare the corpus spongiosum urethra?, make a small opening in the substance of the bulb, next open the dorsal vein of the penis, in it secure a small pipe ; water injected through this will escape at the opening in the bulb : when all the blood shall have been thus washed out, the latter opening may be secured, and some coloured fluid injected along the dorsal vein. If, however, a fine injection be forced from the pudic, or from the internal iliac artery, it may be made to distend the corpora cavernosa penis, and the corpus spongiosum urethras at one and the same time. The student may now detach the crura penis and the neck of the bladder from the pubes, and remove these organs, together with the ure- thra from the subject ; continue an incision from the ante- rior part of the bladder through the upper part of the pros- tate gland, and of the urethra to its extremity ; the mucous lining of the urethra will be thus exposed, the difference in the diameter and other peculiarities in different parts of it may now also be observed. 1st. The prostatic portion is somewhat contracted at either extremity, and dilated in the centre, particularly on the lower surface, and at either side of the middle line ; these enlargements are called the pros- tatic sinuses ; they are separated from each other by a pro- minent fold of the lining membrane, extending from the uvula of the bladder along the mesial line of the urethra, as far as the bulb; this fold is named verumontanum, or caput gallinaginis ; in the centre of it is a very large la- cuna, (sinus pocularis,} the orifice of which is directed for- wards ; on either side of this pouch, and in general exter- nal to it, is the opening of the common ejaculatory duct, external to which, and in the prostatic sinus on each side, are the several small orifices of the ducts of the prostate gland. 3d, The membranous portion is shorter, and of a smaller calibre than the prostatic ; it is cylindrical, its an- DUBLIN DISSECTOR. 229 tenor extremity is the narrowest portion of the canal. 3d, The spongy portion of the urethra is much dilated at first, particularly inferiorly (sinus of the bulb ;) anterior to this the small ducts of the anti-prostatic glands open. The ca- nal of the urethra contracts a little beyond the bulb, and continues of nearly the same diameter until it arrives op- posite the scrotum; it is there slightly contracted for a short distance : about an inch posterior to the external ori- fice of the urethra the canal is dilated in the transverse di- rection; this dilatation is called fossa navicularis ; lastly, the orifice of the urethra is contracted into a narrow vertical slit. Several small lacuna? open on the surface of the mu- cous membrane of the urethra, between the bulb and the anterior extremity, [about sixty-five according to Loder ;] the orifices of these, in a healthy condition of the mem- brane, are very small ; they are all directed forwards : if bristles be introduced into some of these ducts they will be found in many cases to extend backwards for near an inch in the submucous tissue ; these lacunae secrete a thin mucous fluid, which is expelled by the urine in its passage along the urethra ; in chronic diseases of the urethra these ducts not unfrequently become so much enlarged as to ad- mit the end of a small bougie, and so lead to the formation of a false passage : the largest lacunae are on the upper surface of the urethra; one in particular, near the fossa navicularis, is named the lacuna magna.* [If a section of the pelvis be made by dividing it at the symphysis pubis, and one of the sacro-iliac symphyses, leaving the rectum, blad- der &c. in situ, it will be seen that the urethra in its natural position presents two curves, one behind the triangular ligament, which is somewhat concave above, and the other, before the triangular ligament, which presents its convex aspect upwards and forwards ; if then the penis be carried up towards the abdomen, the second curve will be entirely obliterated, and the whole urethra will present a single sweep, the concavity of which looks upwards, hence the curved catheter is more commonly used ; but the straight instrument may be readily + During the dissection of the pelvic viscera, perinoeum, &c. the student should frequently practise the introduction of a catheter into the bladder, which is to be done in the following; manner: the subject lying on iis back with the legs drawn up, the penis should be held, by placing the thumb and index-finger on each side of the corona glandis, by which means the orifice of the urethra will not be com- pressed ; the penis is then to be drawn upwards, and the catheter, being previously oiled, is next to be introduced in a line with the linea alba into the urethra, di- rectly downwards as far as the bulb ; the concavity of the instrument being to- wards the abdomen. The catheter having reached the bulb, its handle is to be depressed by bringing it forwards between the thighs, and in proportion as this is done, the point is elevated, and the catheter glides into the bladder ; in this latter part of the operation, the penis must be allowed to sink down, for if it be kept extended on the instrument, the membranous part of the urethra would be drawn towards the pubes, by which means the introduction of the instrument would be rendered difficult. 20 230 DUBLIN DISSECTOR. introduced by drawing firmly upon the penis, at an angle of forty-five degrees.] The testicle is the seat of many morbid appearances, both in its tunics and in its substance ; hydrocele is very common, this is a dropsy in the serous cavity of the tunica vaginalis ; this latter membrane may be inflamed, and the adhesive process may obliterate its cavity. The tunica albuginea is sometimes the seat of a firm fungus which protrudes through the other coverings to the surface. The testicle and epididymis may be the seat of acute inflamma- tion, as in hernia humoralis the effect of gonorrhoea, also of chronic inflammation with indolent enlargement, or sarcocele. The testis is also the frequent seat of strumous inflammation and suppuration, of fungoid disease in which there is great enlargement, total change of structure and conversion into cerebriform matter ; of true scirrhus and cancer, of hydatid tumours, &c. : these glands are also sometimes atrophied. The spermatic cord is sometimes the seat of encysted hydrocele, of varicocele, particularly on the left side, as also of different tumours. [Another disease in the vaginal cavity is hematocle, or an ac- cumulation of blood, or of blood and serum. Sometimes the inner surface of the tunic is much roughened by the deposition of fibrine. In recent hydroceles, the tunica vaginalis is transparent, but in old cases it is thick and opaque, and sometimes is partially converted into cartilage or even bone. In the radical treatment of hydrocele the great object is to bring about adhesive inflammation, and obliteration of the sac. We sometimes find tubercles in the testicle, either in its substance, or on its surface or in the epididymis, they rarely occur in both testicles at the same time. Hydrocele of the cord sometimes oc- curs from the passage between the abdomen and scrotum, not being completely obliterated at all points.] The prostate gland is seldom found diseased, except in old men; it is rarely inflamed, an abscess however has been met with (unaccompanied by any thickening) in its substance, arising from common inflammation. Scirrhus. The most common disease of the prostate gland is scirrhus ; the gland in its natural state is known to be about the size of a chestnut, but when it is affected with scirrhus, it is often enlarged to the size of the fist. The common ap- pearances observed in scirrhus in other parts of the body, can be plainly seen in this gland; when cut into, it ap- pears to consist of a very solid, whitish, or brown substance, with membranous septa, running through it in various di- rections. According to the degree of enlargement that takes place, the urine is passed through the bladder with greater or less difficulty, as well as an instrument for draw- ing it off. Calculi have been found lodged in the ducts of DUBLIN DISSECTOR. 231 the prostate gland ; they are usually small granules of a dark colour, and give it a mottled appearance when cut into. [Tubercles are occasionally found in the prostate. When this or- gan is enlarged it presents an obstacle to the discharge of urine and even to the passage of the catheter; it sometimes is necessary to in- troduce the finger two inches and a half into the rectum under the prostate, so as to lift up the point of the instrument over the obstruc- tion, which is more commonly on the und>er side of the urethra. In these cases of enlarged prostate the bladder becomes very much con- tracted, and the muscular coat very thick and distinct. This en- largement sometimes occurs in young men from acute inflammation of a gonorrheal character.] The vesiculoe seminales are seldom found diseased; in cases of scrofulous testicle they have been found similarly affected and filled with cheesy fluid. The urethra is the frequent seat of inflammation, which when recent produces suppuration without ulceration, and if long continued, causes a thickening of the submucous tissue, and thus ren- ders the canal narrow and irregular, and so commences the foundation of stricture. [The most common seat of this affection is the membranous part of the urethra, the next most common seat, is about four, or four and a half inches from its orifice, and next just behind the glans penis. The urethra is sometimes malformed ; it may open upon the upper or under surface of the penis, epispadias and hypospadias ; it may termi- nate in the perineum, or above the pubes. All of these malforma- tions do not necessarily imply impotence, sometimes the rectum ter- minates in the urethra of the male, and I have known a case of this kind in which the child lived a year and then died of inflammation, caused by the arrest of an apple seed near the orifice of the urethra.] The coverings of the penis are the frequent seat of ulce- ration, also those of the glans penis ; the latter in old per- sons is very often attacked with warty cancerous ulcera- tion. CHAPTER VII. SECTION L DISSECTION OF THE FEMALE ORGANS OF GENERATION. THE generative organs in the female are more distinct from the urinary than in the male subject ; they may be .divided into the external and internal ; the external parts 232 DUBLIN DISSECTOR. are the mons veneris, vulva, labia, clitoris, nymphse, vagi- na, and perinseum. The mons veneris is an eminence placed on the upper and anterior part of the pubes ; it consists of a quantity of adi- pose substance beneath the integuments, which in the adult are covered with hair. The vulva is the fissure which ex- tends from the mons veneris to within an inch of the anus. The anterior perin&um is the small space in front of the anus, the posterior perinaum is between the anus and the os coccygis. The labia externa or majora, are the thick folds of integument which extend one on each side of the vulva, and are united inferiorly in a crescentic edge, call- ed the commissure or fourchette. The clitoris is below the superior angle or commissure of the labia : it is a small red projection immediately beneath the symphysis pubis and above the vagina ; it is attached by two crura to the rami of the pubes ; these unite and form the body of the clitoris, on the anterior extremity of which is a round red swelling called the glans clitoridis ; this is covered by a thin loose fold of integument or mucous membrane called the prepuce. The clitoris is composed internally of a spongy cellular texture, not very unlike the corpus spon- giosum urethra? in the male subject. The nymphcc, or labia minora, descend one on each side of the vagina, from the prepuce of the clitoris, and are gradually lost about the centre of the vulva. About half an inch below and a little behind the clitoris and between the nymphse, is the round orifice of the mea- tus urinarius ; this opening is surrounded by a projecting fold of mucous membrane, on the sides of which are the orifices of small mucous glands analogous to Cowper's glands in the male. The meatws is from an inch and a half to two inches in length ; it leads backwards and up- wards along the upper surface of the vagina, and is slight- ly curved beneath the symphysis pubis, to which, as also to the crura of the clitoris, it is attached by the triangular ligament. [There are two rules given for the introduction of the catheter in the female ; one is to feel for the clitoris and then to carry the finger down about three quarters of an inch until it rests upon a tubercular elevation, on which the orifice of the urethra will be found : the other rule is to carry the finger directly to the lower edge of the symphysis pubis ; just below which is the tubercle above referred to : this last is the better rule, as by it we avoid as far as possible the handling of the parts ; if the uterus be very much enlarged from disease, or pregnancy, the situation of the bladder and urethra will be changed, so that the latter will lie behind the symphysis and nearly parallel to it, in which case after the point of the catheter is intro- DUBLIN DISSECTOR. 233 duced into the orifice of the urethra, the handle must be depressed far back between the thighs of the patient.] The vagina is directly below the urethra : in the child it is partially closed in front by a crescentic fold of mem- brane, termed the hymen : in the adult several reddish emi- nences [the carunculse myrtiformes] surround this open- ing ; the course and connexions of this canal will be better seen when the pelvis shall have been divided for the pur- pose of examining the internal organs of generation. Dis- sect off the integuments and fascia from the perineum and labia, and the following muscles may be seen : the sphinc- ter ani, levatores ani, and coccygai ; these are similar to the muscles of the same name in the male perinseum, also the transfer sales perin&i : the erectores cliloridis are analogous to the compressores penis ; and the sphincter vagina corres- ponds to the accelatores urinse ; it extends from the clitoris superiorly around each side of the vagina to the central point of the perinseum in front of the anus. To examine the internal organs of generation make a lateral section of the pelvis in the same manner as was di- rected in the dissection of the male pelvis. The perito- naeum may be first examined ; this will be seen to descend along the fore part of the rectum, to within three or four inches of the anus ; it is thence reflected forwards on the posterior part of the vagina, the superior third of which it covers ; from the vagina it ascends on the posterior surface and sides of the uterus ; continues round the superior fun- dus of this organ to its anterior part, on which it descends as low as the commencement of the vagina, it is thence re- flected to the bladder, and is continued over this organ, as in the male subject, to the abdominal muscles ; thus, in the female pelvis, the peritonaeum forms one cul de sac between the rectum and vagina, and another between the uterus and bladder. From each side of the uterus a broad fold of pe- ritonseum is extended transversely towards each iliac fos- sa ; these folds are the broad ligaments of the uterus ; en- closed between the lamin of each of these are the Fallo- pian tube, the round ligament of the uterus, and the ovarium with its ligament and vessels, Dissect off the peritonaeum from one side of the rectum and vagina, and the pelvic vis- cera will be more distinctly seen. The rectum takes the same course as in the male only somewhat more curved, it lies behind the uterus and vagi- na, to the latter it is united by a close vascular plexus. The vagina is seen to surround the neck of the uterus, and thence to descend obliquely downwards and forwards for about six or seven inches between the rectum, the bladder, 20* 234 DUBLIN DISSECTOR. and urethra ; closely connected to the latter, and but loose- ly to the rectum. [The length of the vagina in a healthy state, varies very much in different individuals ; it has been seen but one inch and a half long ; it varies also in the same individual under different circumstances, being about six inches long in the virgin, and about four in the woman who has borne children ; its apparent length also varies at different periods of utero- gestation, owing to the different positions of the uterus ; its capacity also varies very much, being much greater in those who have borne children than in those who have not ; its capa- city however is always greatest at its upper pa.t, where it receives the mouth of the uterus. Its great extensibility is proved during par- turition.] The vagina is lined by a vascular mucous membrane, which is transversely rugose, and is covered externally by a dense fibrous tissue and by numerous vessels, particular- ly veins, which form a plexus (retiform) or spongy body, which is situated beneath the sphincter vaginae muscle ; the vagina is also partially covered by peritoneum on its posterior surface. Between the bladder and vagina the ureter may be observed ; its course is longer and more curv- ed in the female pelvis than in the male. The Uterus is situated between the bladder and rectum, and connected to both by peritonaeum ; the broad ligament which is a fold of peritonaeum, and the round ligament which is a fasciculus of blood-vessels and nerves bound together by dense cellular tissue, connect each side of this organ to the pelvis, and to the inguinal regions. The ute- rus is somewhat pyriform or triangular, the larger end or fundus being superiorly and posteriorly, the smaller end or cervix inferiorly and anteriorly ; the intermediate portion is named the body ; the vagina surrounds the cervix uteri, and ascends higher posteriorly than anteriorly ; at the lower extremity of the cervix is a small transverse slit, termed the os uteri or os tinea* [It is -bounded by the lips of the uterus of which ths anterior is the thickest, and is continuous with the anterior wall of the vagina, while the posterior is thinner and longer, and is attached by its base to the posterior wall of the vagii-a, hence it projec's into the latter organ, which forms behind it a large cul de sac. The uterus varies much in size in chr.ldhood, youth, and adult life ; it is larger and firmer in those who have borne children than in those who have not. It is from twelve to fourteen lines long at birth, and but an inch and a half long, at ten years of age, so that it is aimost stationary, until the age of puberty at which period it is suddenly and rapidly developed, and filled for its future functions. In the adult female the average size of the organ is as follows; length two and a half to three inches; breadth at the fallopian tubes an inch and a half, at the neck six to twelve lines ; thickness ten to twelve lines ; medium thickness of the DUBLIN DISSECTOR. 235 parietics of the body five lines, of the neck four, thickness of the lips three to four lines ; heighth of fundus above the fallopian tubes a quarter of an inch. The weight of the organ averages at puberty from six to ten drachms ; in the adult from one and a half to two ounces, and at the full term of utero-gestation from one and a half to three pounds. The cavity of the body of the uterus is an equilateral triangle flat, tened antero-posteriorly, with its sides convex internally, its diameter is about ten lines at its greatest, and much less at the angles ; the cavity of the neck is about an inch long with a diameter of three or four lines, it is somewhat cylindrical in form, but wider at its centre than its extremities ; the sides being concave towards each other. The situation of the uterus varies very much with the period of life and of utero-gestation, in the fetus and infant it is in the cavity of the abdomen.] The uterus consists of a dense fibrous substance, perfo- rated by a great many vessels, covered externally by peri- tonaeum, and lined throughout by mucous membrane, which is continued from the vagina throughout the entire organ, and thence into the Fallopian tubes, along which it ex- tends to their fimbriated extremity, where it becomes con- tinuous with the peritonaeum on each side, thus presenting a singular example of the continuity of a mucous and se- rous "membrane with each other: the mucous membrane of the uterus is often of a very dark colour, and is marked by several lines. The cavity of the uterus is very small, and somewhat triangular, being larger in the superior fun- dus than elsewhere. The Fallopian tubes are from four to five inches in length ; they extend from the fundus uteri upwards and outwards at lirst, and then a little downwards and backwards ; each ter- minates in a soft fringed extremity, called Corpus fimbria- tum, which communicates with the cavity of the peritoneum and which overhangs the ovary ; these canals are narrow where they join the uterus, but each increases in size near the corpus fimbriatum. The ovaria are two small, white, flattened, oval bodies, one at each side, enclosed in the pos- terior fold of the broad ligament, and behind the Fallopian tube ; their surface is often irregular and as it were cica- trized. Each ovary is connected to the side of the uterus by the broad ligament of the latter, also by a round fibrous cord, the proper ligament of the ovary ; this is about two inches long, and is enclosed between the laminae of the broad ligament of the uterus. Each ovary is covered by the peritonaeum, which adheres very closely to it ; beneath this is a strong white fibrous capsule, within which a num- ber of small vesicles will be found connected together by cellular membrane and vessels. [The ovaries vary in size with age, and they are proportionably 236 DUBLIN DISSECTOR. large in the foetus and child ; their average size in eight females, be- tween the ages of seventeen and twenty-three was found to be, length seventeen lines, breadth nine lines, thickness four lines and a half, and weight one drachm and a quarter : they are heavier in those who have borne children than in others. The ovaries of women who have had children present upon their surfaces, cicatrices which cor- respond to certain bodies internally, which are called the corpora lutea and which are supposed to be the debris of impregnated ova. The female organs of generation present many anomalies of confor- mation. The uterus and vagina are sometimes a solid mass having no cavity, the uterus is sometimes entirely wanting either with or without a corresponding deficiency of the tubes and ovaries, gene- rally however the latter is the case : the uterus is sometimes divided by a longitudinal septum into two cavities, which open separately into the same vagina or each has its own vagina : the uterus may present two horns or cornua as in many of the inferior animals : it may also be absolutely double, the two organs opening into a common vagina, each into its own vagina, or one into the vagina and the other into the rectum : the mouth of the uterus is sometimes completely obliterated, of this I have a specimen from a female between fifty and sixty years of age ; perhaps the cases of superfoetation, may be explained by referring to some of the anomalies above mentioned. One ovary is sometimes wanting, the other being larger than usual ; the fallopian tubes may be imperforate. The vagina is sometimes solid, sometimes imperforate, from the presence of the hymen or an anomalous septum, it is sometimes double, sometimes it communi- cates with the bladder, and at other times with the rectum ] The female organs of generation are the seat of many morbid changes. Not to notice the various ulcerations to which the external parts are liable, we occasionally find here also polypi, adipose and sarcomatous tumours in the labia, enlargement of the clitoris, &c. The uterus may be found inflamed, (matritis), this oc- curs soon after parturition, the adjacent peritonaeum is also generally affected ; the uterus itself exhibits the same ap- pearances as the inflammation of the substance of other parts ; the inflammation is found to creep along the Fallo- pian tubes and ovaries. It often advances to suppuration, and pus is generally found in the large veins of the womb. When the peritonaeum is inflamed, it has been remarked, that the extravasated fluid and coagulabie lymph are found in a greater proportion to the degree of inflammation, than in common peritonitis. Polypus. Polypi are very fre- quently found in the uterus ; they may grow at any period of life, but they are rarely met with in the young. By a polypus is meant a diseased mass, which adheres to the cavity of the uterus, by a sort of a neck or narrower por- tion. Polypus is of two different kinds ; the most common kind is hard, and consists of a substance divided by thick membranous septa ; this sort of polypus varies very much DUBLIN DISSECTOR. 237 in its size, some not being larger than a walnut, and others being larger than a child's head. Another sort of polypus forms in the uterus, which consists of an irregular bloody substance, with tattered processes hanging from it ; when cut into it appears to be a spongy mass, holding large cells. The most common part to which polypi adhere, is the fun- dus uteri, and sometimes they are found attached to the os tineas. Hard fibrous tumours also not unfrequently exist in the parietes of the uterus. The uterus is also frequently the seat of cancer, which usually commences near the os tincse. The uterus also is subject to partial displacement, viz. prolapsus, inversio, and retroversio. The membrane covering, or the substance of the ovary, are very rarely found inflamed, except when they are in- cluded in general peritonitis ; when the inflammation pro- ceeds from the uterus, it sometimes goes on to the forma- tion of pus in the ovary. Dropsy. The most common dis- ease in the ovary is dropsy, the whole snbstance of the ovarium is sometimes converted into a capsule containing fluid. When the ovaria have become dropsical, their nat- ural structure has disappeared, and they are found convert- ed into cells, communicating with one another by consider- able openings, and very much enlarged : the ovaria are sometimes converted into a series of cysts, which have no communication with each other ; these cysts have been confounded with hydatids, to which they bear some resem- blance ; they are however very different ; they have much firmer and less pulpy coats than hydatids, they contain a different kind of fluid, and they are differently connected among themselves. Hydatids either lie unconnected, or one large one encloses a number of small ones ; while ovarian cysts adhere to each other by broad surfaces, and do not enclose each other. The ovaria are sometimes found converted into cysts, holding large masses of fat, hair, and some teeth ; these substances appear to be gene- rated by the internal membrane of the cyst ; the hairs are most of them loose in the fatty substance, but many of them adhere to the inside of the capsule ; the teeth, which are not always perfect, are sometimes attached to the cyst, and at others, to an irregular mass of bone. 238 DUBLIN DISSECTOR. CHAPTER VIII. DISSECTION OF THE INFERIOR EXTREMITIES. EACH inferior extremity is connected to the trunk by the strong ligaments of the hip joint, and by several muscles which pass from the pelvis to the thigh and leg. This dis- section may be performed while the pelvis remains attach- ed to the spine, or the former may be separated from the lumbar vertebrae, and divided into two. [The muscles of the inferior extremity are very differently arranged from those of the superior. The great locomotive functions of the inferior extremities are progression, and retrogression, accordingly we find that the flexor and extensor muscles, are on opposite sides of the limb, and that they change their relative position in each subregion of the extremity; while in the superior extremity the flexor muscles are all on the same aspect of the limb, and so too with the extensors. Besides flexion and extension, the motions of these extremities, in- elude rotation inwards and outwards, adduction and abduction, which movements are effected either by special and appropriate muscles, or by certain of the flexors and extensors : of the former fact, we have an illustration, in the rotator muscles of the thigh ; of the latter in the tibiales anticus and posticus ; the former flexes the foot upon the leg, the latter extends it, yet both together, turn the foot inwards and upwards. As in the case of the upper, so in the lower extremities, the muscles should be classed as nearly as possible according to their functions, and we find that they may be examined in the four regions of the hip, the thigh, the leg, and the foot ; this arrangement has reference to the part of the extremity, upon which the muscle chiefly lies; again in the several regions the muscles are arranged in classes having reference to the particular part of the limb on which they act, and lastly the classes are divided into groups, according to the par- ticular and principal motion effected by their contraction as flexion extension, &/c. In proceeding with the muscles which act upon the inferior extremity, we examine first the region of the hip, in which we find but one class of muscles, all acting upon the thigh, these are twelve in number, on each side, arranged in three groups, the flexors three, the extensors three, and the rotators six, as follows. First Group, Flexors. The psoas parvus is inserted here rather as a matter of expediency, than propriety, not because it is a flexor of the thigh but from its position, and because it is in some respects a congener of the psoas magnus. 1. Psoas Parvus, ) T7 -., in _ 2. Psoas Magnus, ( Vlde P' 195 ' 3. Iliacus Inlernus, Vide p. 196. DUBLIN DISSECTOR. 239 Second Group, Extensors. 1. Gluteus Maxim us, Vide p. 254. 2. Gluteus Medius, " 255. 3. Gluteus Minimus, " 256. Third Group, Rotators. 1. Pyriformis, Vide p. 256. 2. Obturator Interims, " 257. 3. Obturator Externus, } 4. Gemellus Superior, > Vide p. 259. 5. Gemellus Inferior, S 6. Quadratus Femoris, Vide p. 258. Of these groups the first is situated anteriorly, for the most part in the abdomen ; the second and third are posteriorly, on and about the dorsum of the ilium, and are found in three layers, in the first the gluteus maximus, in the second the gluteus medius, and in the third the gluteus minimus, anteriorly and superiorly, and the six rotators posteriorly and inferiorly. The muscles on the region of the thigh are fifteen in number, on each side, and are arranged in two classes, one acting upon the leg, the other upon the thigh ; in the first class there are three groups, the superficial group of three muscles, the flexors four, and the extensors also four ; in the second class there is but one group, of four muscles, the adductors. FIRST CLASS. First Group. Three superficial muscles at the outer, fore, and inner part of the thigh. 1. Tensor vaginae femoris, an abductor and rotator } of the thigh, and which acts upon the outside of the > Vide p. 245. leg, through the fascia lata. i 2. Sartorius, a flexor of the leg, and adductor of the whole limb. 3. Gracilis, a flexor of the leg and adductor. Vide p. 249. Second Group. Four extensors of the leg, situated on the anterior aspect of the thigh. 1. Rectus Femoris, which also flexes the thigh upon the pel vis. 2. Vastus Externus, Vide p. 247. 3. Vastus Internus, " 248. 4. Crureus or Cruralis, beneath which at the lower ) part of the thigh, is sometimes found the Subcrureus. \ Third Group. Four flexor muscles of the leg, situated on the posterior aspect of the thigh. 1. Biceps Flexor Cruris, Vide p. 261. 2. Semi-Membranosus, " " 262. 3. Semi-Tendinosus, " " 261. 4. Popliteeus, " 273. 240 DUBLIN DISSECTOR. SECOND CLASS, ONE GROUP. Four adductor muscles situated at the inner, back, and fore part of the thigh, and most of which also assist in flexion of the thigh upon the pelvis. 1. Pectineus, Vide p. 249. 2. Adductor Longus, " " 250. 3. Adductor Brevis, " " 250. 4. Adductor Magnus, " " 251. The muscles on the region of the leg are twelve in number on each side, and are arranged in two classes : the first class acts upon the foot as a whole, and consists of three groups, one group posteriorly which extends the foot upon the leg, a second group along the fibula, and a third group along the tibia, in which two groups some of the muscles are flexors, and some extensors of the foot upon the leg. The second class consists of two groups which act primarily upon the toes, and if their action be continued, secondarily upon the foot. FIRST CLASS. First Group. Three extensor muscles of the foot, situated on the posterior aspect of the leg. The two first by their fleshy bellies forming the calf of the leg, and lower down joining to form the tendo achillis. 1. Gastrocnemius, Vide p. 271 Second Group. Three muscles situated along the fore, back, and outer part of the fibula, of which the first and second extend the foot, and abduct it, also causing its external edge to look upwards, while the third flexes the foot, but is in other respects a congener of the other two. 1. Peroneus Longus, Vide p. 269 2. Peroneus Brevis, " " 269. 3. Peroneus Tertius, " " 268. Third Group. Two muscles situated along the tibia, one anterior and the other posterior to the interosseous ligament ; the first flexes the foot, the second extends it, but both together adduct it, and cause the internal edge to look upwards. 1. Tibialis Anticus, Vide p. 267. 2. Tibialis Posticus, " 274. SECOND CLASS, TWO GROUPS. First Group. Two extensors of the toes, and flexors of the foot, situated ante- riorly. 1. Extensor Digitorum Longus, Vide p. 267. 2. Extensor Pollicis Proprius, " " 268. DUBLIN DISSECTOR. 241 Second Group. Two flexors of the toes and extensors of the foot, situated posteriorly. 1. Flexor Longus Digitorum Perforans, Vide p. 273. 2. Flexor Pollicis Longus, " 275. In connexion with the different, varieties of club foot or talipes, we find a shortening of the tendons of these muscles on the region of the leg, the particular tendons affected, depending upon the particu- lar direction of the deformity. At first sight it would appear, as if certain muscles would be concerned in the production of talipes varus, the most common form, and certain other muscles, in the pro- duction of talipes valgus ; for example in the first case, the tibial muscles and the flexors of the toes ; in the second case, the two pero- neals, long and short, &c. : but experience goes to prove that in the operation for club foot, it is rarely necessary to divide any thing ex- cept the tendo achillis, after which the shortening and rigidity of the other tendons may be overcome ; by the proper application and con- tinuance of the machine and the shoe. Out of one hundred and eighty cases of club foot, Dr. Detmold found it necessary to divide the tendo achillis alone, in one hundred and sixty-lhree, in the other seventeen cases, it was necessary to divide the tendo achillis and other tendons. On the region of the foot on either side we find twenty muscles, which all act upon the phalangeal bones, except the transversalis pedis, which acts rather upon the phalangeal extremities of the me- tatarsal bones. These muscles are arranged in two classes, the one acting upon the toes generally, the other upon individual toes. In the first class are two groups, chiefly common extensors, and flexors of the toes : in the second class also are two groups, the proper mus- cles of the great toe, and the proper muscles of the little toe. FIRST CLASS. First Group. One muscle only, situated on the superior or dorsal surface of the foot. 1. Extensor Brevis Digitorum Pedis, Vide p. 268. Second Group. This group consists of fourteen muscles, situated on the plantar surface of the foot, for the most part. Some of them however, are between the metatarsal bones, and may be seen both on the plantar and dorsal surfaces of the foot, viz. the seven interossei. Some of these muscles are single, while others are manifold, viz. the four lum- bricales and seven interossei. 1. Flexor Brevis Digitorum Pedis Perforatus, Videp.276. 2. Flexor Digitorum Pedis Accessorius, ) ,7-. 977 3. to 6. The Four Lumbricales, $ y ' 1. Transversalis Pedis, which is somewhat analogous " to the palrnaris brevis of the hand, except that the lat- ter arches the hand at the carpus, while the former ^Videp.278. arches the foot at the phalangeal extremity of the metatarsus. 21 242 DUBLIN DISSECTOR. 8 to 14. The seven Interossei, of which four are seen*| on the dorsal surface of the foot, three on the plantar surface, and of these last, the third or most external, is > Vide p. 279. the adductor of the little toe. All seven of these mus- I cles are adductors and abductors of the four lesser toes. J SECOND CLASS. First Group. Three muscles at the under surface and inner edge of the foot which act upon the great toe only. 1. Abductor Pollicis Pedis, Vide p. 276. 2. Flexor Brevis Pollicis Pedis, ) v . fl _ Q 3. Adductor Pollicis Pedis, j^***- " Second Group. Two muscles at the under surface and outer edge of the foot, which act upon the little toe only 1. Flexor Brevis Minimi Digiti, Vide p.%18. 2. Abductor Minimi Digiti, to which may be added } y. , ^g the third inferior interosseous muscle under the name of, > 3 Adductor Minimi Digiti. ) " " 280. We find then on taking a review of all the muscles, which operate directly on the inferior extremity, that there are on the region of the hip anteriorly and posteriorly twelve muscles ; on the region of the thigh, fifteen, without the subcruralis ; on the region of the leg twelve ; and on the region of the foot twenty ; in all fifty-nine muscles for each extremity, or one hundred and eighteen for both. We find too that though each muscle exercises what may be considered its chief and leading motion, still its action is modified by its own course, by its combination with other muscles, and by its own extent, as for ex- ample we find that when a muscle arises in one region, and passes over a second to be inserted into a third, it will act upon both regions, but produce a different and opposite motion in the two ; as in the case of the rectus femoris, which arises from the pelvis, passes over the whole length of the thigh, and is finally inserted into the leg, through the patella and its ligament. The leading action of this muscle is to extend the leg upon the thigh, but having done that it can then flex the thigh upon the pelvis. So too with many other muscles of the extremities.] SECTION I. DISSECTION OF THE MUSCLES OF THE THIGH. PLACE the extended limb on the back part, raise the in- teguments from the anterior and lateral parts of the thigh, DUBLIN DISSECTOR. 243 and from the upper part of the leg; several cutaneous nerves, veins, and lymphatic vessels are met with in this dissection ; the nerves are branches of the lumbar plexus, and of the anterior crural nerve ; they pierce the fascia lata near Poupart's ligament, and descend chiefly along the anterior and outer side of the thigh. The cutaneous veins are branches of the internal saphena vein ; this vessel will be found, in dissecting the leg and foot, to commence at the inner side of the latter, and to ascend along the internal part of the leg and knee to the inner and forepart of tho thigh, along which it continues its course towards the groin ; and about an inch and a half or two inches below Poupart's ligament it pierces the fascia lata, and joins the femoral vein. In this course the saphena vein receives several cutaneous branches, and, in general, just before it ends in the femoral it is joined by one or two large veins from the outer and forepart of the thigh, and by some smaller branches from the abdominal parietes ; some cu- taneous branches from the anterior crural and lumbar nerves accompany this vein in its course along the thigh. Beneath the integuments the thigh is invested by the su- perficial fascia, which is prolonged around it from the parietes of the abdomen ; in the groin this fascia is thick and laminated, and closely connected to the fascia lata, particularly to its cribriform portion; but inferiorly and posteriorly it is thin and loose, and differs but little from the ordinary sub-cutaneous cellular tissue. This fascia may be easily detached from the fascia lata of the thigh, except in the groin ; in attempting to raise it in this region we expose the superficial inguinal ganglia ; these are eight or ten in number : five or six of them are placed parallel to Poupart's ligament, some above, others below it ; two or three are situated lower down in the groin than these, near the termination of the saphena vein ; these last ganglia lie on the fascia lata ; they are larger than the former, and are parallel to the saphena vein. Through these conglo- bate inguinal ganglia the superficial absorbents of the low- er extremities pass ; also those from the external parts of generation. Beneath the fascia lata, and close to the fe- moral vessels, are the deep-seated inguinal ganglia ; they are small, and only three or four in number; the deep- seated absorbents of the limb pass through these. The in- teguments and superficial fascia having been removed, the fascia lata may be next examined. This aponeurosis sur- rounds the thigh ; it is very strong and tendinous external- ly, but so thin and weak internally, that without caution it is apt to be removed along with the integuments ; it is at- tached superiorly and externally to the crest of the ilium ; 244 DUBLIN DISSECTOR. posteriorly to the sacrum and coccyx : on the glutseus max- imus it is very weak and thin, but at the anterior border of this muscle it becomes very strong, receiving an addition of fibres, both from the tendon of that muscle, and from the tensor vaginae femoris ; anteriorly the fascia lata is at- tached to Poupart's ligament, and internally to the rami of the ischium and pubis ; as this aponeurosis extends- down the thigh, it confines the different muscles in their situation, so as to preserve the figure of the limb ; several processes also pass in from its internal surface to form septa and sheaths for some muscles, and to bind down others in their place ; to many of these processes the muscles adhere, so that when in action they serve to make the fascia more tense and resisting ; these processes also serve to increase the surface of origin or attachment of several muscles. Along the posterior part of the thigh the fascia lata is. con- nected to the whole length of the linea aspera, also to the insertion of the glutasus maximus, and to the origin of the short head of the biceps ; inferiorly it adheres to the con- dyles of the femur, surrounds the knee-joint, and receives an addition of fibres from the different tendons in this re- gion ; below the knee it is continued over the heads of the tibia and fibula into the fascia of the leg. Numerous fora- mina are observable in the fascia lata, particularly at the upper and anterior part of the thigh ; they transmit cuta- neous nerves and vessels: the most remarkable of these holes is that for the saphena vein ; it is situated about an inch and a half or two inches below Poupart's ligament, and may be most distinctly seen by dividing the vein on the forepart of the thigh, and raising it towards the abdo- men ; this opening is semilunar, the concavity directed up- wards ; from its apparently sharp edge the fascia is reflect- ed backwards, and is lost on the sheath of the femoral ves- sels. That part of the fascia which is internal to this open- ing is named the pubic portion of the fascia lata ; it covers the pectinseus muscle, adheres to the spine and linea in- nominata of the pubis, extends behind the femoral vessels, and is continuous with the fascia iliaca ; that part of the fascia lata external to the saphenic opening is called the iliac portion ; it covers the sartorious, tensor vaginse, rec- tus, and iliacus internus muscles, and- is continued ob- liquely in front of the femoral vessels, in the form of a cre- scentic or falciform process, the concavity of which is direct- ed downwards and inwards ; the convexity is towards the ilium, and attached to Poupart's ligament ; the lower -cornu of this crescentic process is continuous with the outer cor- nu of the saphenic opening, and the upper cornu extends in front of the femoral vessels to their inner side, and is DUBLIN DISSECTOR. 245 inserted along with the third insertion of Poupart's liga- ment, or Gimbernaut's ligament, into the linea innominata, or ilio pectinaea. Between the margin of the falciform process and the pubic part of the fascia lata is a thin mem- brane, perforated by numerous vessels, this is termed the cribriform fascia, it is connected on either side to the iliac and pubic portions of the fascia lata, and extends from the saphena vein to Poupart's ligament, in front of the femoral vessels ; it adheres to the anterior part of the sheath of the latter, or to the fascia transversalis ; when this cribriform fascia is removed, the falciform process is made more dis- tinct. (See Description of Crural Hernia, page 150.) The fascia lata, in some situations, particularly along the outer side of the lirnb, is seen to consist of two laminae of fibres ; the external take a circular, the internal a longitudinal di- rection ; these two laminae are very distinctly separated at the upper and outer part of the thigh by the insertion of the tensor vaginas femoris ; the deep layer, which in this situation is very strong, is attached to the capsular liga- ment of the hip joint, and to the external head of the rec- tus muscle, Raise the fascia lata from the anterior and lateral parts of the thigh, several muscles will come into view, the femoral vessels also in the groin will be partially exposed, they are still somewhat concealed by a quantity of adipose substance, and by a few deep-seated lymphatic ganglia ; when these are removed, we always find the vein internal to the artery, and about an inch and a half from the spine of the pubis; immediately external to the vein is the artery resting on the psoas, and about a quarter of an inch external to the artery is the anterior crural nerve, im- bedded between the psoas and i'liacus, and covered by the fascia iliaca, it does not, therefore, lie in the sheath of the vessels. Clean the several muscles which now partially appear on the forepart of the thigh ; external to the ves- sels, the sartorius and tensor vaginae are first seen ; inter- nal to the vessels are the pectinaeus, graoilis, and the three adductors, and immediately covering the anterior and lateral parts of the femur are the rectus, erurseus, vastus internus, and externus. MUSCLES ON THE FOREPART AND SIDES OF THE THIGH. These are eleven in number. 1. TENSOR VAGINAE FEMORIS, at the upper and outer part of the thigh, narrow above, broad and thin below, arises tendinous and fleshy from the external part of the anterior superior spinous process of the ilium ; it forms a fleshy belly, which descends obliquely backwards, and is inserted, broad and thin, into a duplicature of the fascia lata on the 21* 246 DUBLIN DISSECTOR, outside of the thigh, about three inches below the great trochanter ; use, to make tense the fascia, to rotate the thigh inwards ; also, to assist in flexing and abducting it. The origin of this muscle is between the sartorius and gluteeus medius : between these muscles it descends, covered by the fascia lata ; its insertion is anterior to that of the glutseus maximus muscle. 2. SARTORIUS is the longest muscle in the body, thin and flat like a ribband, broader in the middle than at the ex- tremities, situated obliquely along the anterior and inner side of the thigh, arises by short tendinous fibres from the anterior superior spine of the ilium, and from the notch below that process, it soon becomes broad and fleshy, ex- tends obliquely across the thigh to its inner side, and de- scending perpendicularly to the knee passes behind the condyle of the femur ; it then turns forwards and outwards towards the inner side of the upper end of the tibia, into which it is inserted below the tubercle, by a long flat tendon, the anterior edge of which is attached to the fascia lata covering the knee-joint, and the posterior edge sends off' an aponeurosis to the fascia of the leg. Use, to flex the leg upon the thigh, also the latter on the pelvis; to adduct the thigh and leg obliquely, so as to cross the lower extremi- ties ; when the thigh and leg arc extended, it assists in rais- ing and advancing forwards the whole limb, also in turning the knee outwards ; in standing, it also supports the pelvis and prevents it bending backwards on the thigh. This muscle through its whole extent is covered only by the fascia lata and the integuments, its superior extremity lies between the tensor vaginse and the iliacus internus mus- cles ; its inferior extremity expands into a strong aponeu- rosi.s, which covers and adheres to the tendons of the semi- tendinosus and gracilis muscles, anterior and superficial to both of which it is inserted ; in its course along the thigh it first passes over the psoas, iliacus, and rectus muscles, next over the vastus internus and adductor muscles and the femoral vessels, from which it is separated by a strong aponeurosis; iriferiorly it passes over the internal lateral ligament of the knee, between the tendons of the adductor magnus and the gr-acilis. The superior third of this mus- cle extends in an oblique direction from the ilium down- wards and inwards, forms the external boundary of the in- guinal region, and lies to the outer side of the femoral ves- sels ; the middle third is more vertical in its course, and is here about two inches broad, and completely covers the femoral vessels, also a part of the adductor, and vastus in- ternus muscles. [Varieties. Meckel saw one subject in which this muscle was DUBLIN DISSECTOR. 247 wanting. In the negro, it is sometimes found unusually broad, and sometimes it presents a middle tendon.] 3. RECTUS FEMORIS, long and flat, rather round in the centre, placed vertically on the forepart of the thigh, arises by two tendons, one short, strong, anterior and internal, from the anterior inferior spinous process of the ilium, the other longer, broader, and more curved from the superior and external border of the acetabulum, and from the capsular ligament ; these tendons soon uniting form a strong fleshy belly, which descends almost vertically, with a slight inclination inwards; this muscle has a peculiar penniform appearance, it is also tendinous anteriorly in the upper half, so that the sartorius can glide over it, and tendinous posteriorly in the lower half, whereby it can move on the surface of the crurceus. This muscle ends in a flat ten- don, which is inserted along with the vasti and cruraeus into the upper edge of the patella, a few fibres pass ante- rior to this bone, and are continued into the ligamentum patellae, which descends obliquely outwards to the tuber- cle of the tibia. Use, to extend the leg on the thigh, and to flex the thigh on the pelvis ; it also supports and draws forwards the pelvis on the thigh, and strengthens the cap- sular ligament of the hip joint. The anterior tendinous origin of this muscle is covered by the sartorius, tensor vaginse, and iliacus internus muscles, the posterior by the glutseus medius and minimus muscles; the remainder of the muscle is only covered by the integuments and fascia ; su- periorly this muscle lies on the capsular ligament of the hip joint and the external circumflex vessels; in the rest of its course on the crurseus and vasti muscles, to which it is united below, so that some describe these four as one. muscle, under the name of quadriceps extensor cruris. Be- neath the rectus we find this large mass of muscular sub- stance, covering the front and sides of the femur ; it may be divided superiorly into three portions, but infcriorly these are inseparably united ; the external portion is nam- ed vastus externus, the internal, vastus internus, and the middle, crurssus. 4. VASTUS EXTERNUS, much larger than the other portions, and larger above than below, arises tendinous and fleshy from the root and anterior part of the great trochanter, an- terior to the tendon of the glu'toeus maxlmus, from the outer edge of the linea aspera, its whole length, and from the oblique ridge which leads to the external condyle, anterior to the short head of the biceps ; from all the external sur- face of the bone, and from the fascia lata, the fibres des- cend obliquely forwards; the superior are very long, the inferior are shorter and more transverse, inserted into the 248 DUBLIN DISSECTOR. external surface of the tendon of the rectus, also into the side of the patella, and by an aponeurosis, which adheres to the synovial membrane of the knee-joint, into the head of the tibia. Use, to extend the knee, also to rotate the leg outwards ; this muscle is partly concealed by the rectus ; its external surface is tendinous above and fleshy below, its internal is fleshy above and tendinous below. 5, VASTUS INTERNUS, smaller and shorter than the last, arises on the anterior part of the femur, from the inter-tro- chanteric line ; from the inner edge of the linea aspera, its whole length, also from the inner side of the femur, the fibres descend obliquely forwards, and are inserted into the inner edge of the tendon of the rectus, also into the patel- la, and by an aponeurosis, which covers the inner side of the synovial membrane of the knee, into the head of the tibia. Use, to extend the knee and turn the leg a little in- wards. The vastus internus is partly concealed by the rectus and sartorius, its origin lies anterior to the insertion of the psoas, pectinceus, and adductor muscles, and over- laps the cruraus, so as to be in contact with the vastus ex- ternus ; its internal surface is tendinous above and fleshy below ; an aponeurosis from the two vasti covers the patel- la and its ligament, also the sides of the joint ; this apone- rosis is inserted into the head of the tibia, it serves to sup- port the patella in its situation, and to protect the sides of the articulation like a capsular ligament ; a small bursa is situated over the patella, between this aponeurosis and the skin ; the insertion of the vastus externus into the patella overlaps that of the vastus internus, and both overlap the crurseus, from which the vastus externus can be more easi- ly separated above, but the vastus internus below. 6. CKURVEUS, shorter than either of the vasti, between which it lies, larger and more tendinous below than above, arises fleshy from the anterior and external part of the fe- mur, commencing at the inter-trochanteric line, and ex- tending along three-fourths of the bone, as far outwards as the linea aspera ; it does not adhere to the inner side of the femur, there being a portion of the latter, nearly an inch in breadth and extending almost the whole length of the bone, to which no muscular fibre adheres ; the crurceus descends close to the femur to its inferior third, the fibres then incline forwards, become tendinous posteriorly, and are separated from the bone by a large bursa, and by a considerable quantity of fat ; inserted into the upper and outer edge of the patella, also into the synovial membrane of the knee behind the vasti, particularly the external, to which it is here intimately united. Use to assist the vasti and the rectus in extending the leg. This muscle is cover- DUBLIN DISSECTOR. 249 ed by the rectus and the vasti, from the latter it can only be separated superiorly by tearing a few muscular fibres, and tracing some large nerves and vessels that pass be- tween them. The large bursa, which is situated behind the lower part of this muscle, is attached to and frequently communicates with the synovial membrane of the joint; a few muscular fibres are generally attached to this mem- brane, and have been described as a distinct muscle, the SUB-CRURAL or CAPSULAR, this arises from the anterior sur- face of the femur, about its inferior fourth, passes forwards and downwards, and is inserted into the synovial mem- brane. Use, to raise the synovial membrane in extension of the leg, so as to prevent its being contused by the pa- tella. 7. GRACILIS, flat, long, and thin, broad and fleshy above, round and tendinous below, situated at the inner side of the thigh, immediately beneath the integuments and fascia ; arises by a thin short tendon from the lower half of the symphysis, and from the inner edge of the descending ra- mus of the pubis ; it soon becomes fleshy, and descends ver- tically, one edge directed forwards, the other backwards, and its surfaces looking one inwards, the other outwards ; about the inferior fifth of the thigh it ends in a round ten- don which passes behind the inner condyle, and then turns forwards along with the tendon of the sartorius. behind and beneath which it lies ; inserted into the superior part of the internal surface of the tibia, uniting with the sartorius and semi-tendinosus, but superficial to the latter. Use, to adduct the leg and thigh, to bend the knee, and turn the leg and foot inwards. The origin of the gracilis is between the triceps and the cms penis ; its whole course is superficial, except near the knee, where it is covered by the sartorius ; its insertion is inferior to that of the sartorius, and superior to that of the semi-tendinosus ; the saphena vein and nerve are situated between its tendon and that of the sartorius at the inner side of the knee, but these are separated from each other by a fascia, which attaches these tendons toge- ther, the vein lying superficial : from the tendon of the gra- cilis an aponeurosis is sent off to the fascia of the leg. a PECTIN^EUS, flat, triangular, broad above, situated at the superior, anterior, and internal part of the thigh ; arises fleshy from the linea innominata and the concave surface below it on the horizontal rarnus of the pubis, between the spine of that bone and the ilio-pectina3al eminence ; it forms a flat fleshy belly, which descends obliquely out- wards and backwards, and is inserted by a flat tendon into the rough ridge which leads from the lesser trochanter to the linea aspera. Use, to adduct and flex the thigh, also, 250 DUBLIN DISSECTOR. to rotate it outwards ; it may also serve to strengthen the capsular ligament of the hip joint internally, and in ad- duction of the limb to draw the capsule inwards from be- tween the neck of the femur and the acetabuluin. The pectinseus lies between the psoas magnus and the adductor longus; the latter overlaps it; it is covered superiorly by the fascia lata, and inferiorly by the femoral vessels ; it covers the obturator nerve and vessels, the external obtura- tor muscle, and the adductor brevis ; it also adheres to the capsular ligament of the hip joint. [Variety. A fissure sometimes divides this muscle into two, of which the lower part is the smallest.] TRICEPS ADDUCTOR FEMORIS consists of three portions, which pass in distinct laminas from the pelvis to the thigh. 9. ADDUCTOR LONGUS, flat and triangular, broad below", is situated at the upper and internal part of the thigh, su- perficial to the other adductors and to the pectinseus ; it arises by a short, small, but strong tendon from the anterior surface of the pubis, between its spine and the symphysis ; this ends in a broad fleshy belly, which descends obliquely backwards and outwards, and is inserted by a broad thin tendon into the middle third of the linea aspera, between the adductor magnus and the vastus internus, to both of which it is closely united. The origin of this muscle lies between the pectinceus and the gracilis, and above the ad- ductor brevis ; its insertion is behind the vastus internus, and in front of the adductor magnus ; this adductor is co- vered by the integuments and fascia superiorly, and by the sartorius and the femoral vessels inferiorly ; it lies anterior to the two following muscles. [Varieties. This muscle is sometimes divided into two, by a fis- sure, and sometimes its insertion extends lower down than above de- scribed, by its tendon running into that of the adductor magnus.] 10. ADDUCTOR BREVIS, short, flat, and triangular, is situ- ated posterior to the adductor longus and pectinseus, and internal to the psoas ; arises flat and tendinous from the anterior inferior surface of the pubis, between the gracilis muscle, the symphysis pubis, and the thyroid hole ; it soon ends in a fleshy belly, which passes outwards, backwards, and a little downwards, inserted by tendinous slips into the superior third of the internal root of the linea aspera, ex- tending for about three inches below the lesser trochanter. The origin of this muscle is external to the gracilis, and concealed by the adductor longus and the pectinceus ; as it descends it is covered by these muscles, except a small por- tion near its insertion, which appears between them ; this portion is posterior to the femoral and prof unda vessels ; DUBLIN DISSECTOR. 251 its insertion is anterior to that of the adductor magnus ; in the tendon of this adductor one or two large openings fre- quently exist for the passage of some of the perforating arteries. [Variety. This muscle also is sometimes divided into two by a fissure, which according to Meckel, is analogous to the same muscle in the ape. The same is also true of the next muscle.] 11. ADDUCTOR MAGNUS, the longest and largest of the ad- ductors, triangular, the base attached to the femur, the apex to the pelvis ; arises chiefly fleshy from the anterior surface of the descending ramus of the pubis, external to the gracilis, also from the ramus of the ischium, and ten- dinous from the external border of the tuberosity of the latter ; the fibres pass outwards with different degrees of obliquity ; those which arise from the pubis ascend ob- liquely outwards, those from the ramus of the ischium pass outwards and downwards, and those from the tuber ischii more directly downwards ; inserted fleshy into the rough ridge which leads from the great trochanter to the linea as- pera, tendinous and fleshy into the linea aspera, and by a long round tendon into the internal condyle of the femur. The superior edge of this muscle has a twisted appearance, it is nearly parallel to the quadratus femoris ; several branches of the internal circumflex vessels pass between these muscles, and in rotation of the leg inwards the lesser trochanter projects between them; the middle portion which is inserted into the linea aspera, is internal to the in- sertion of the glutseus maximus, and to the origin of the short head of the biceps. This part of the muscle is per- forated by several branches of the perforating arteries ; at the lower part of the linea aspera this muscle appears to separate into two portions, one of which is inserted into the linea aspera, between the vastus internus and the short head of the biceps ; the other is continued into the long tendon which is inserted into the inner condyle. The ad- ductor magnus is covered internally by the gracilis, and anteriorly by the long and short adductors, the pectinseus, part of the sartorius, and the femoral vessels ; posterior to it are the sciatic nerve, and the hamstring muscles ; the tendinous insertion of the lower part of this muscle is in- timately connected to the vastus internus : about the infe- rior fourth of the thigh there is a large oblique opening be- tween these two muscles, through which the femoral ves- sels pass into the poplitseal space, Use, the three adduc- tors, in addition to adducting the limb, can rotate it out- wards ; they also serve to steady and support the pelvis on the thigh ; the long and short adductors can also flex the 252 DUBLIN DISSECTOR. thigh on the pelvis, and the adductor magnus can extend it, when it has been flexed. In dissecting the preceding muscles, we observe the fol- lowing vessels and nerves. The Femoral Artery passes from under Poupart's ligament about midway between the symphysis pubis and the spine of the ilium ; it thence descends obliquely inwards and backwards, and about the lower part of the middle third of the thigh it perforates the tendon of the adductor mag- nus, enters the poplitoeal space, and then receives the name of poplitseal artery. In the upper third of the thigh, or in the inguinal region, the artery is covered only by the skin, superficial fascia, some lymphatic ganglia, and the fascia lata ; in the middle third of the thigh it receives the addi- tional covering of the sartorius, and beneath this of a very strong tendinous aponeurosis, which passes from the ten- dons of the adductor longus and magnus over the artery and vein, and joins the tendon of the vastus internus ; in this part of the thigh the artery is enclosed in a perfect tendinous sheath, consisting anteriorly of the aponeurosis just mentioned, posteriorly and internally of the tendons of the adductors, and externally of the vastus internus : at the lower end of the sheath the artery passes into the ham through a large oval opening which is bounded supe- riorly by the adductor longus and magnus, externally by the vastus internus, internally by the adductor magnus, and inferiorly by the united tendons of the adductor mag- nus and vastus internus. The femoral artery in this course first passes over a few fibres of the psoas, next over the pectinseus and adductor brevis, the adductor longus, and a small portion of the magnus. The femoral artery, immediately below Poupart's liga- ment, gives offi 1st, some cutaneous branches ; 2nd, small arteries to the inguinal ganglia; 3rd, about two inches be- low Poupart's ligament, a very large branch, the profunda i 4th, several muscular branches to the sartorius and vastus internus ; and 5th, just before it enters the ham the anasto- motica magna, which is distributed to the muscles and inte- guments at the inner side of the knee. The profunda is the largest branch of the femoral ; it descends behind that ves- sel and to its inner side, and gives several branches to the muscles of the thigh, namely, the external and internal cir- cumflex, and the three or four perforating arteries. (See Anatomy of the Vascular System.) The femoral vein takes the same course as the artery ; in the groin it always lies to its internal or pubic side, but as it descends it becomes posterior to it. In dissecting the muscles on the fore part of the thigh, numerous branches of the anterior crural nerve DUBLIN DISSECTOR. 253 are met with ; this nerve in the groin is separated into se- veral branches, many of these become cutaneous, others pass to the muscles on the fore part of the thigh, and two or three accompany the femoral artery ; one of these, the nervus saphenus, enters its tendinous sheath, and descending along the fore part of the artery, as far as the opening in the tendon of the triceps, then leaves that vessel, descends between the tendons of the sartorius and gracilis muscles to the inner side of the knee ; it there becomes cutaneous, and attaching itself to the saphena vein, it accompanies this vessel along the inner side of the leg to the internal ankle. (See Anatomy of the Nervous System.) SECTION II. DISSECTION OF THE POSTERIOR PART OF THE THIGH. PLACE the detached extremity on its fore part, with a block beneath the hip joint, so as to flex the latter slightly, and thus extend the muscles in this region. Raise the inte- guments from the posterior surface of the limb, from the crest of the ilium to the calf of the leg ; the cutaneous nerves which are met with in this dissection are branches from the lumbar nerves, from the sacral plexus, and from the sciatic nerve. The cutaneous veins pass in different directions, some turn round the inner side of the limb to the saphena vein, others penetrate between the muscles, and join the deep veins which accompany the muscular or the perforating arteries, and others descend to the popliteal space, and join the popliteal or the lesser saphena vein. The fascia lata over the glutaeus maximus is weak, but an- terior to that muscle, that is, covering the glutseus medius, it is very strong and adheres to the surface of this muscle, and to the crest of the ilium above it ; on the posterior part of the thigh, the fascia is not so dense as on the outer or anterior part ; inferiorly, over the popliteal region, or the ham, it is much stronger than above ; from the thigh it is continued over the muscles of the leg, in which situation it may be examined afterwards : the fascia and integuments being removed, the muscles should be cleanly dissected ; these may be divided into the muscles of the hip and of the 22 254 DUBLIN DISSECTOR. DISSECTION OF THE MUSCLES OF THE HIF. These are nine in number, viz. the three glutsei, the pyri- formis, the gemini, the two obturator, and the quadrator femoris. 1. GLUTJEUS MAXIMUS covers the greater part of the pel- vis, also the upper part of the thigh ; it is somewhat square, one edge being the origin and attached to the sacrum, the opposite edge or the insertion to the femur, and to the fas- cia lata, the other edges are directed one upwards and for- wards, the other downwards and backwards. The inferior edge is thick and round, and covered by a great quantity of fat ; this forms the fold of the nates. It is difficult to clean the surface of the glutseus maximus, its fasciculi are so coarse and rough, this may be facilitated by dissecting parallel to the fibres, that is, in a line drawn from the sa- crum towards the great trochanter. This muscle arises by fleshy and short aponeurotic fibres, from the posterior fi'fth of the crest of the ilium, from the rough surface be- tween the crest and the superior semicircular ridge on this bone, from the posterior sacro-iliac ligaments and lumbar fascia, from the tubercles on the posterior surface of the sacrum, the side of the coccyx, and from the great sciatic ligaments, which last it covers : the fibres are collected into distinct fasciculi, which descend obliquely outwards and forwards, nearly parallel to each other, converging a little towards the thigh ; the lower fibres are the longest, they all form a strong and dense mass, particularly below, and end in a flat and thick tendon, whose external surface is rough and coarse, but the internal smooth, and lined by a bursa which separates it from and allows it to glide over the great trochanter, this tendon is inserted into a rough ridge which leads from the trochanter to the linea aspera, also into the upper third of that line, and by a tendinous expansion into the fascia lata, covering the vastus externus muscle. Use, to extend the thigh, also to abduct and rotate it outwards, to support and extend the pelvis and the trunk on the lower extremity, also to make tense the fascia lum- borum and the fascia lata. The glutseus maximus is co- vered by the integuments, by a considerable depth of fat, and by a thin fascia ; as the latter approaches the upper edge of the muscle, it becomes more strong and adherent, and is thence extended over the anterior part of the glutseus medius, to which it adheres very closely, and is then in- serted into the crest and anterior spine of the ilium. The glutseus maximus covers the tuber ischii and all the mus- cles on the posterior part of the pelvis, except the anterior portion of the glutseus medius, which is covered by the DUBLIN DISSECTOR. 255 fascia just now mentioned ; its insertion into the linea as- pera is above the short head of the biceps, and between the vastus externus and adductor magnus ; a very large bursa lines its tendon, and is expanded over the trochanter and a portion of the vastus externus; it is very thin, it usually contains much synovial fluid, and it is frequently intersected by tendinous bands ; a smaller bursa is often situated below it, between the tendons of the glutseus maxi- mus and vastus externus. Divide this muscle by a perpendicular incision, and se- parate the edges ; several muscles, vessels, &c. may be no- ticed, having the following relation to each other ; com- mencing above, we see the glutseus medius muscle, beneath this, the pyriformis, and between these, the glutceal vessels and the superior glutseal nerve ; below the pyriform mus- cle we remark the great sciatic and some smaller nerves, also the sciatic and pudic vessels, all escaping from the pelvis by the lower part of the sciatic notch ; next in order are thegemclli muscles surrounding the tendon of the obtu- rator internus, below these is the quadratus femoris, paral- lel to the superior fibres of the abductor magnus ; the great sciatic ligament, the tuber ischii, and the superior attachment of the hamstring muscles are seen in this dissec- tion, also several small arteries and veins, and a considera- ble quantity of loose watery cellular tissue, which sur- rounds the sciatic nerve in its course, through the depres- sion between the trochanter and tuber ischii. 2. GLUT^EUS MEDIUS, triangular, flat, thinner than the last described muscle, is exposed by dividing the glutseus maxi- mus and dissecting off the strong fascia which extends from its anterior edge to the crest of the ilium, arises by fleshy and aponeurotic fibres from the deep surface of this fascia, from the three anterior fourths of the outer edge of the crest of the ilium, from the superior semicircular line or ridge which leads from the anterior spinous process of the ilium to the upper part of the sciatic notch, and from the surface of the ilium, above and below that ridge ; the fibres descend in different directions, the middle perpendicularly, the an- terior, which are very short, and the posterior, which are long, obliquely ; they all converge into a strong and broad tendon, which is inserted into the upper and outer part of the great trochanter, and is attached anteriorly to the ten- don of the glutseus minimus. Use, to abduct the thigh ; its posterior fibres can extend and rotate it outwards, its ante- rior fibres can flex and rotate it inwards ; it also serves to maintain the pelvis in equilibrio on the femur, as when standing on one leg. This muscle is covered in part by the glutseus maximus ; the anterior and larger portion is 256 DUBLIN DISSECTOR. covered only by the integuments and fascia lata ; it lies on the glutseus minimus, its posterior edge is parallel to the pyriform muscle, and separated from it by the glutaeal ves- sels and nerves ; the anterior edge is nearly parallel to and behind the tensor vaginse muscle, is united to it above, but separated from it below by a quantity of fat, and by seve- ral branches of the external circumflex vessels and nerves. 3. GLUT^EUS MINIMUS, is exposed by detaching from its origin the glutseus medius ; small, semicircular, more ten- dinous than the last, it arises from the inferior semicircular ridge on the dorsum of the ilium, and from the rough sur- face between it and the edge of the acetabulum ; the fibres converge as they descend, and end in a strong round twist- ed tendon, which is inserted into the upper and anterior part of the great trochanter, first passing over a small bur- sa. Use, similar to the last, it also strengthens the ilio-fe- moral articulation, and as it adheres to the capsular liga- ment, it can draw this out of the joint in abduction of the thigh. This muscle is covered by the glutseus medius, and a little overlapped by the tendon of the pyriformis, it covers the capsular ligament and the external tendon of the rectus. 4. PYRIFORMIS, is of a flattened triangular form, the base at the sacrum within the pelvis, the apex at the trochanter ; situated partly within the pelvis, partly behind the hip joint, nearly parallel to the posterior border of the glutasus minimus ; it arises within the pelvis by three tendinous and fleshy fasciculi, from the anterior or concave surface of the second, third, and fourth divisions of the sacrum ; it also receives a few fibres from the anterior surface of the great sciatic ligament, and from the upper and back part of the ilium ; the fibres form a thick fleshy belly, which passing through the great sciatic notch, descends obliquely out- wards and a little forwards, and is inserted by a round ten- don into the upper part of the digital fossa, at the root of the great trochanter above the tendons of the gemelli,and obturator muscles, to which it is connected. Use, to abduct the thigh, to extend and rotate it outwards, it can also act on the capsular ligament in the same manner as the glu- tseus minimus. Within the pelvis this muscle lies on the sacrum and is covered by the hypogastric vessels, the scia- tic plexus of nerves, and the rectum ; the sciatic nerve of- ten perforates it, near its lower margin ; on the dorsum of the pelvis this muscle is covered by the glutseus maximus, and is parallel to, but not covered by the glutseus medius ; it adheres to the rnpsular ligament, and is superior to the gemelli,from which it is separated by the sciatic nerve and vessels ; this muscle divides the sciatic notch into two parts, through the superior pass the glutseal vessels and nerves, DUBLIN DISSECTOR. 257 through the inferior the sciatic and pudic vessels, the scia- tic nerve and several smaller branches of the sacral plexus of nerves. To expose the following five small rotator mus- cles of the hip joint, draw to either side the great sciatic nerve, and remove the surrounding loose cellular tissue. [Variety. This muscle is sometimes divided by the great sciatic nerve as it passes out of the pelvis. So far as I have observed, this occurs most commonly, when there is also an anomaly of the nerve itself, which consists in its high bifurcation, one trunk coming out in the usual situation, beneath the pyriform muscle, and the other, perforating the muscle.] 5, 6, GEMELLI, two small muscles behind the ilio-femoral articulation between the ischium and the trochanter, the SUPERIOR arises narrow and fleshy from the spine of the ischium : the fibres pass outwards above the tendon of the obturator internus, and are inserted with it into the upper part of the digital fossa of the great trochanter. INFERIOR arises also fleshy, from the upper part of the tuber ischii, and from the great sciatic ligament, the fibres run parallel to the former, and are also inserted into the digital fossa. Use, to rotate the thigh outwards, also to abduct it, to strengthen the capsular ligament and to confine the obtu- rator tendon in its situation. These muscles are concealed by the ghita3us maximus and the sciatic nerve ; they are placed between the pyriformis and the quadratus femoris muscles : they form a sort of sheath around the tendon of the obturator internus, and adhere to its edges; they appear as portions of this muscle added to it as it escapes from the pelvis : the inferior is the larger of the two : the superior is inserted between the pyriformis and the obturator inter- ims, and the inferior between the tendons of the obturator internus and externus : they both adhere to the capsular ligament. [ Varieties. These muscles are both wanting in some subjects ; in others one only, the superior, is wanting, which is said to be analo- gous with the ape.] 7. OBTURATOR INTERNUS, is situated partly within the pel- vis and partly behind the ilio-femoral articulation ; some- what triangular, the base within the pelvis, the apex at the great trochanter, arises by aponeurotic and fleshy fibres within the pelvis from the superior or pelvic surface of the obturator or thyroid ligament, and from all the circumfe- rence of the foramen of that name, except at the upper part where the obturator nerve and vessels pass through : beneath these a ligamentous arch is extended, and from this some fibres of this muscle proceed ; it also arises from the pubis internally, and from the ischium inferiorlv, and 22* 258 DUBLIN DISSECTOR. from a thin but strong fascia of the same name, which co- vers this muscle and separates it from the levator ani mus- cle ; the fibres descend obliquely outwards and backwards, converging towards the lesser sciatic notch, which is be- tween the spine and the tuberosity of the ischium ; the fibres here end in a flat tendon, which turning outwards, winds round the cartilaginous pully-like surface which the ischium here presents ; a loose bursa, and one, in general, containing a quantity of synovia, is here interposed be- tween this tendon and the bone ; the tendon now runs out- wards on the dorsum of the pelvis, between the gemelli muscles, and is inserted into the digital fossa of the great trochanter. Use, to abduct and rotate the thigh outwards ; it may also act on the capsular ligament. This muscle within the .pelvis is covered by the peritoneum, the pelvic fascia, levator ani muscle, and by a strong aponeurosis, termed the obturator fascia, which serves to give origin to some fibres both of the obturator muscle and of the levator ani, between which it is interposed ; the obturator fascia is the external layer of the pelvic fascia ; it adheres supe- riorly to the ilium and pu bis, and is inserted interiorly into the great sciatic ligament, into the tuberosity and ramus of the ischium, also into the ramus of the pubis, it here be- comes continuous with the triangular ligament of the urethra ; this fascia is closely connected to the obturator internus muscle, except inferiorly where the internal pu- dic nerve and vessels intervene. As the obturator tendon is passing through the sciatic notch, its deep surface is di- vided into four or five distinct tendons, which are lined by the synovial membrane, and connected to each other like so many plaits or folds ; the pudic vessels lie external to this tendon in this situation ; the continuation of the tendon to its insertion has the same relations as the gemelli muscles. 8. QUADRATUS FEMORIS, arises by fleshy and aponeurotic fibres from the external surface of the tuber ischii, anterior to the tendon of the semi-membranosus, the fibres pass transversely outwards, and are inserted tendinous and fleshy into the inferior and posterior part of the great trochanter, and into the posterior intertrochanteric line. Use, to ad- duct and rotate the thigh outwards : this muscle is covered by the glutseus maximus and sciatic nerve ; its origin is also 'concealed by the hamstring muscles ; it is parallel to and between the gemelli and the adductor magnus ; its low- er border is overlapped by the latter ; it covers the obturator extemus, the lesser trochanter, and the insertion of the psoas and iliacus. Divide this muscle, and a little dissection will expose the following, particularly if the gracilis, adductor, and pectina3us muscles have been previously removed. DUBLIN DISSECTOR. 259 [Varieties. This muscle is sometimes wanting. Very rarely it is found to consist of a large number of fasciculi, it is more prone than many muscles, to a fatiy transformation.] 9. OBTURATOR EXTERNUS, situated at the superior, pos- terior, and internal part of the thigh, somewhat triangular or pyramidal, the base towards the pubis, the apex at the trochanter, arises fleshy from the inferior surface of the thyroid or obturator ligament, and from the surrounding surface of the pubis and ischiurn, the fibres descend ob- liquely outwards and backwards behind the -neck of the femur, in a sort of notch or groove between the tuber ischii and the edge of the acetabulum; here they end in a strong tendon, which ascends a little behind the neck of the femur, then runs directly outwards along the inferior gemellus, and adhering to the capsular ligament, is inserted into the lower part of the digital fossa. Use, to adduct the thigh, and to rotate it outwards ; it also supports and strengthens the inferior and posterior part of the ilio-femoral articula- tion, particularly in abduction of the thighu This muscle is placed in a very deep situation, being covered, anteriorly, by the adductor brevis and pectinseus, also by the obtura- tor nerve and vessels, internally by the adductor muscles, externally by the joint, .and posteriorly by the quadratus femoris and gluta3us rnaximus. The several small muscles just described, in addition to their individual actions, effect the common purpose of strengthening the ilio-femoral articulation. The capsular ligament of this joint is covered anteriorly by the rectus, psoas, and iliacus ; internally by the pectinseus and obtu- rator externus ; externally by the tendon of the rectus, the glutaeus minimus arid .medius, posteriorly by the pyriform, gemelli, obturator tendons quadratus femoris, and glutseus maximus, and inferiorly by the tendon of the obturator ex- ternus. Many of these muscles, like the small capsular muscles of the shoulder joint, guard Against dislocation in the different motions of the limb, and also serve to protect the capsular ligament by drawing it out of the angle which is formed between the acetabulum and the neck of the fe- mur in the rotatory motion of the limb. In dissecting the foregoing muscles, several vessels and nerves must have been remarked; the former are derived from the hypogastric or internal iliac vessels ; the latter from the sacral plexus of nerves ; the arteries are the glu- taeal, sciatic, and pudic. The glutaal artery escapes through the upper part of the sciatic notch, above the pyriform muscle, and immediately divides into several branches; these are distributed to the three glutaei muscles. The sciatic artery passes out of the pelvis through the lower part 260 DUBLIN DISSECTOR. of the great sciatic notch, below the pyriformis ; its prin- cipal branches descend between the tuber ischii and the great trochanter, and are lost in the surrounding muscles. The pudic artery escapes from the pelvis along with the last described vessel; it soon, however, re-enters the cavity through the lesser sciatic notch, and pursues its course for- wards and inwards towards the perinseum and pubis, lying at first on the internal surface of the obturator internus, and afterwards on the rami of the ischium and pubis, its branches are distributed to the external organs of genera- tion, and to the muscles in the perinseum. (See Anatomy of the Vascular System.) Each of these arteries have their corresponding veins, which take a similar course, and terminate in the internal iliac vein. The nerves which are found in this situation are the superior and inferior glutaeal, the posterior cutaneous, the pudic, the great and lesser sci- atic ; these are all branches of the sacral plexus. The su- perior glutaal nerve accompanies the glutsoal artery, and is distributed principally to the glutseus medius and minimus muscles. The inferior glut&al nerve escapes below the py- riform muscle, and is distributed principally to the glu- toeus maximus. The inferior or lesser sciatic nerve accom- panies the last through the sciatic notch, descends obliquely inwards round the tuber ischii, and is distributed to the surrounding muscles and integuments. The posterior cuta- neous nerve also passes through the lower part of the great sciatic notch, descends beneath the glutosus maximus, and then becoming cutaneous, divides into several long branch- es, which may be traced along the posterior surface of the thigh, even to the leg, where in general they will be found to communicate with the posterior cutaneous nerves of that region. The pudic nerves take the same course as the pudic artery, and terminate in corresponding branches. The great sciatic or posterior crural nerve, is the largest nerve in the body ; it passes out of the pelvis below, but often through the pyriform muscle, descends behind the hip joint in the fossa between the trochanter and tuber ischii, cover- ed by the glutseus maximus, and passing over the gemelli, obturator, and quadratus muscles ; its course along the back of the thigh, and its branches, shall be considered after the dissection of the following muscles. DISSECTION OF THE MUSCLES ON THE BACK PART OF THE THIGH. THE fascia in this situation has been already noticed ; the muscles are only three in number, and are commonly called hamstring muscles ; the semi-tendinosus and semi- DUBLIN DISSECTOR. 261 membranosus form the inner, the biceps the outer ham- string. BICEPS FLEXOR CRURIS, consists of a long and short, head ; the LONG HEAD arises from the outer and back part of the tuber ischii in common with the semi-tendinosus, this descends obliquely outwards, and soon ends in a thick fleshy belly ; about the inferior third of the thigh it joins, at an acute angle, the SHORT HEAD, which arises fleshy from the linea aspera, between the vastus externus and the ad- ductors, commencing below the insertion of the glutseus maximus, and continuing to within two inches of the exter- nal condyle ; here the muscle ends in a strong tendon, which descends at first behind the knee, then turns forwards and outwards towards the head of the fibula, into which it is inserted ; the tendon is here divided in general by the ex- ternal lateral ligament into two fasciculi, the superficial of which, in addition to its attachment to the head of the fibula, is also inserted into the fascia of the leg ; and the deep fas- ciculus which is also inserted into the fibula, sends some fibres to the head of the tibia. Use, to flex the knee-joint, also, by its long head, to extend the thigh and rotate the whole limb outwards ; the long head can also fix the pelvis, and prevent it and the trunk from bending forwards on the head of the femur. The superior fifth of this muscle is concealed by the glutseus maximus, the remainder is co- vered by the integuments and fascia, and descends between the vastus externus and semi-tendinosus, forming the outer hamstring ; the long head passes over the semi-membra- nosus, the sciatic nerve, and the triceps muscles ; it also conceals the short head : inferiorly the biceps passes over the external articular vessels and the external head of the gastrocnemius muscle, and forms the outer hamstring. [ Varieties. The short head is sometimes wanting which is analo- gous to some of the inferior animals ; sometimes there is a slender third head from the tuber ischii, or the long head, which runs down the leg into the tendo achillis ; this is analogous to other mammalia.] 2. SEMI-TENDINOSUS, large, flat, and fleshy above, round and tendinous below, arises by fleshy fibres from the tu- berosity of the ischium in common with the long head of the biceps, also from the inner or anterior edge of the ten- don of the latter for about three inches ; it descends ob- liquely inwards, and about four inches above the knee it ends in a long round tendon, which passing behind the head of the tibia, is then reflected forwards between the tendon of the semi-membranosus and the internal head of the gastrocnemius, and is inserted into the anterior angle of the tibia below its tubercle, inferior and posterior to the 262 DUBLIN DISSECTOR. tendons of the gracilis and sartorius, to which it is connect- ed : from the convex edge of the tendon an aponeurosis is given off, which joins the fascia of the leg. Use, to flex the knee and rotate the leg inwards, to extend the thigh, to sup- port the pelvis, and prevent the trunk falling forwards. This muscle is covered superiorly by the glutasus maximus ; the rest of its course is superficial, a transverse line usual- ly intersects it about its centre. [Variety. This muscle is sometimes divided into three parts, by two transverse tendinous lines.] 3. SEMI-MEMBRANOSUS, beneath the semi-tendinosus, flat and aponeurotic superiorly, thick and fleshy in the middle, round and tendinous below ; arises by a flat tendon from the upper and outer part of the tuber ischii ; this descends obliquely inwards, ends in a fleshy belly, which retains this muscular structure lower down than either of the former muscles, a little above the knee it ends in a round tendon, which passes behind the internal condyle, and divides into three processes, one of which passes outwards, another downwards, and a third forwards; the first is a broad aponeurosis, which ascends obliquely outwards, beneath the heads of the gastrocnemius muscle over the back part of the knee-joint, and is inserted into the external condyle of the femur ; this aponeurosis has been termed the poste- rior ligament of the knee-joint, or the ligament of Winslow ; the second is a strong and broad fascia, which descends over the poplitseus muscle, and is inserted into the posterior part of the heads of the tibia and fibula, and is also con- tinuous with the fascia of the leg ; the third process ap- pears the continuation of the tendon, it turns forwards be- neath the internal lateral ligament, round the head of the tibia, into which it is inserted. Use, to extend the thigh on the pelvis, and to support the latter on the thigh, to flex the knee and to rotate the leg inwards ; it also strengthens the back part of the knee, and can draw the synovial mem- brane out of the angle of the joint. This muscle, at its origin, lies external to the other hamstring muscles; it is covered at first by the semi-tendinosus, biceps, and glutseus maximus, inferioiiy it is superficial ; above, is passes over the quadratus femoris and adductor magnus muscles ; be- low it overlaps the popliteal vessels, and the internal head of the gastrocnemius, from which last it is separated by a bursa ; the sciatic nerve is on its outer, the gracilis on its inner side. [This muscle together with the last forms the inner hamstring.] The arteries which are met with in the dissection of these muscles are branches of the sciatic, circumflex, perforating, DUBLIN DISSECTOR. 263 and articular, the numerous ramifications of these vessels are distributed to the hamstring and adductor muscles, and are accompanied by their corresponding veins ; the prin- cipal nerve in this situation is the great sciatic ; from the back part of the hip joint this large nerve descends along the back of the thigh to the upper part of the popliteal space, where it divides into the peronseal and posterior tibial nerves; in this course it is covered at first by the glutreus maximus, afterwards by the biceps and semi-ten- dinosus, and inferiorly by the integuments and fascia ; hav- ing passed over the quadratus femoris and the other small muscles at the back of the hip joint, it next lies on the ad- ductor magnus, and inferiorly on a quantity of adipose sub- stance. The sciatic nerve gives oif several cutaneous and muscular filaments, in addition to its two terminating branches, the peronseal and the posterior tibial ; the peron- (cal nerve takes the course of the biceps tendon towards the head of the fibula, where it divides into several branches which are distributed to the integuments and muscles on the outer and forepart of the leg, as will be described in the dissection of that region. The posterior tibial nerve ac- companies the popliteal vessels through the space of that name, which space the students should next examine. The popliteal space is situated behind the knee-joint, ex- tending upwards for about one-fourth of the thigh, and downwards for about one-sixth of the leg; it is somewhat oval, is bounded internally by the inner hamstring, and the internal head of the gastrocnemius ; externally by the biceps, external head of the gastrocnemius, and the plan- taris; it is covered by the integuments and by a strong fascia, which, derived from the fascia lata, is strengthened by adhering to the condyles of the femur, and to the ad- joining tendons ; this fascia serves to approximate the sides of this region, and thus to give to it a considerable depth. The popliteal space is bounded before by the flat surface of the femur, by the back part of the joint covered by the ligament of Winslow, by the head of the tibia, and by the poplitasus muscle ; in this region are contained the termi- nating branches of the sciatic nerve, the popliteal artery and vein with their branches ; also some lymphatic ganglia and much adipose substance. The nerves are superficial and external to the vessels, that is, nearer to the biceps ; the vessels are close to the bone, and near to the semi- membranosus muscle, the vein being superficial and a little to the outer side of the artery ; two or three lymphatic ganglia are connected to the latter ; and a quantity of fat, which is of a peculiar soft consistence, intervenes between the nerve and vessels. The course of the perona3al nerve 264 DUBLIN DISSECTOR. has been already noticed ; the posterior tibial nerve descends nearly vertically between the hamstring muscles and the heads of the gastrocnemius, and then runs beneath the sol- seus, and over the poplitseus ; above it lies to the outer side of, and at some distance from, the artery, but below it is in close contact with it, and to its tibial or inner side, it then accompanies the posterior tibial vessels down the leg, and along the inner side of the heel, to the sole of the foot, in which course it shall be examined afterwards ; in the ham this nerve sends off muscular branches, also the posterior or external saphenus nerve, which accompanies the posterior saphena vein along the back of the leg, towards the outer ankle, behind which it passes to the external and superior part of the foot, where it is distributed ; this nerve is by some called "communicans tibialis." The popliteal artery descends obliquely outwards through this space, and at the lower edge of the poplitseus muscle divides into the ante- rior and posterior tibial arteries ; in this course it sends off many muscular and five articular branches, the latter sup- ply the ends of the bones, and the sy no vial membrane of the knee-joint. The popliteal vein accompanies the artery, lying superficial and somewhat external to it ; it receives branches which correspond to those of the artery ; and it is joined inferiorly by the lesser or posterior saphena vein. Next proceed to the dissection of the leg. SECTION III. DISSECTION OF THE LEG. REMOVE the integuments of the leg and foot; on the plantar surface of the latter they are always remarkably hard and thick, even in the foetus, particularly beneath the heel and the first and last joints of the toes ; in these situ- ations also the subcutaneous fat has a peculiar granulated structure, being intersected by tendinous bands, which pass from the skin to the plantar fascia. Beneath the in- teguments of the leg we find two cutaneous veins, the in- ternal and external saphena ; the internal saphena is large and regular, and has numerous branches ; it commences by small veins from the upper surface of the toes, and from the dorsum of the foot ; these run towards the inner malleolus and unite in one large vessel, which ascends along the inner side of the leg, receiving in its course nu- DUBLIN DISSECTOR. 265 merous branches from the integuments ; it then passes be- hind the inner condyle of the femur, and ascending along the inner and anterior part of the thigh, it terminates in the femoral vein about an inch and a. half below Poupart's ligament ; on the thigh this vein is accompanied by small nerves, which are derived from the lumbar plexus and from the anterior crural ; along the leg the saphenus nerve, a branch of the anterior crural, is attached to it, and winds round it. The posterior or external saphena vein commences behind the external ankle from the junction of several small veins from the integuments of the heel and sole of the foot ; it ascends along the surface of the gastrocnemius muscle, accompanied by the communicans tibialis nerve ; at the ham this vein in general joins the popliteal vein, but sometimes it here turns inwards and joins the internal sa- phena vein, with which it always communicates in its course along the leg. Several cutaneous nerves are dis- tributed to the leg, namely, the internal saphenus, from the posterior tibial, and several cutaneous branches from the peronseal and anterior tibial nerves perforate the fascia of the leg on its outer and anterior part, and are distribu- ted to the integuments of the leg and foot. The fascia of the leg is derived partly from that of the thigh ; it also receives additional fibres from the tendons around the knee-joint, namely, the rectus and vasti ante- riorly ; the vastus externus and biceps externally ; the sar- torius, gracilis, and inner hamstring internally ; the fascia adheres to the head of the tibia and fibula, to the spine of the tibia, near its whole length, to the annular ligaments of the ankle joint, and to the malleoli ; it can scarcely be said to exist on the anterior surface of the tibia, which is only covered by the skin and periosteum. The fascia of the leg is stronger superiorly than inferiorly ; near the ankle it again increases in strength from its connexion to the malleoli and to the annular ligaments ; these are two in number, the anterior and internal. The anterior annular ligament is a little above the joint ; it is somewhat square, and stronger externally than internally ; in the latter situ- ation it is attached to the malleolar process of the tibia, and to the os naviculare ; in the former to the external malleolus, and to the upper part of the os calcis ; it con- sists of two layers, which, by separating and re-uniting, from three rings or sheaths for the tibialis anticus, and the two extensor tendons ; the anterior tibial vessels and nerves also pass beneath it. The internal annular ligament is broad- er than the anterior ; it is attached to the internal malleo- lus, and to the os catcis ; it forms a sort of arch over the groove or canal in which the three flexor tendons, and the 2o 266 DUBLIN DISSECTOR. plantar nerves and vessels run. The fascia of the leg is thin posteriorly ; near the heel it is indistinct : on either side it is connected to the sheaths of the tendons that pass round the rnalleoli ; and on each side of the tendo Achillis it sends in a lamina to join the fascia which covers the deep muscles of the leg. The fascia serves to confine the muscles in their situation, and to give origin to many of their fibres ; this last effect is further accomplished by inter- muscular bands or septa, which pass in from the fascia, between the extensor and peronsei muscles, and are attach- ed to the tibia and fibula and interosseous ligament. From the anterior annular ligament, a thin fascia is extended over the dorsum of the foot ; that covering the sole of the foot, the plantar fascia, is remarkably strong ; it arises from the extremity of the os calcis, narrow but thick and strong ; it passes forwards, expands and divides into three parts, which lie on different planes, and which, by sending in two processes, serve to separate the plantar muscles into three orders, the internal, middle, and external ; the lateral portions of this fascia are attachad to the sides of the tar- sus and metatarsus ; the internal portion is the weakest : the middle division is the strongest, and on a plane inferior to the internal ; as this middle portion expands beneath the plantar muscles, it is strengthened by transverse fibres, and near the base of the toes it divides into five fasciculi, these diverge, and opposite the head of each metatarsal bone, they each sub-divide into two fasciculi ; these pass along the sides of the metatarso-phalangeal articulations, and are inserted into the lateral ligaments of these joints, and into the sheaths of the flexor tendons ; between these fasciculi the tendons pass, also the digital vessels and nerves of each toe : the plantar fascia possesses the same strength as ligamentous structure ; use, it serves to retain the arched form of the foot, and to protect the plantar mus- cles, vessels, and nerves, from pressure ; it also gives at- tachment to several muscular fibres. The muscles of the leg may be divided into those on the anterior, external, and posterior part. DISSECTION OF THE MUSCLES ON THE ANTERIOR AND EXTERNAL PART OF THE LEG. THE muscles on the forepart of the leg are four in num- ber, viz. the tibialis anticus, extensor pollicis, extensor communis, and peronseus tertius ; the muscles on the outer side of the leg are the peronseus longus and brevis ; almost all these muscles are connected to each other superiorly, so that they cannot be perfectly separated from each oth- er ; they all adhere to and partly arise from the fascia of DUBLIN DISSECTOR. 267 the leg, therefore, when exposed, they present a rough sur- face superiorly. 1. TIBIALIS ANTICUS, is next the tibia, somewhat triangu- lar, large and fleshy above, tendinous below, arises tendi- nous and fleshy from the outer part of the two superior thirds of the tibia, from the head of the fibula, from the inner half of the inter-osseous ligament, from the fascia of the leg, and from the intermuscular septa ; the fibres des- cend obliquely inwards, end in a strong and flat tendon which crosses from the outer to the forepart of the tibia, runs through a distinct ring in the annular ligament, near the internal malleolus, passes forwards and inwards above the astragalus and naviculare, increases in breadth, and is inserted into the inner side of the great or internal cunei- form bone, also, by a tendinous slip into the base of the first metatarsal bone or that of the great toe. Use, to flex the ankle, to adduct the foot, and to raise its inner edge from the ground ; to turn the toes inwards, also to support the leg when standing, and prevent it bending backwards. This muscle is superficial through its whole length ; the tendon, at its insertion, is partly concealed by the abductor and flexor pollicis brevis ; superiorly this muscle is exter- nal to the tibia ; inferiorly it is anterior to it : the extensor communis, and extensor pollicis, the anterior tibial vessels and nerves are to its outer or fibular side, a small bursa separates its tendon from the upper part of the internal cuneiform bone ; another bursa in general surrounds it, as it is passing over the synovial membrane of the ankle joint. 2. EXTENSOR DIGITORUM LONGUS, arises tendinous and fleshy from the external part of the head of the tibia, from the head of the fibula, and from about three-fourths of this bone, from part of the inter-osseous ligament, from the fas- cia of the leg, and its intermuscular septa ; the fibres des- cend obliquely inwards ; a liitle below the middle of the leg they end in three flat tendons, which pass under the annular ligament through a ring common to these and to the peronseus tertius, and extend forwards over the dorsum of the foot, the internal of the three tendons here divides into two ; the four tendons now extend along the dorsum of each of the four external toes, the great toe does not re- ceive any, and are inserted into the last phalanx of each. Use, to extend the toes and flex the ankle. This muscle is superficial; superiorly, it lies between the tibialis anticus and peronseus longus, and is connected to both; in the middle of the leg it is between the extensor pollicis and perona?us brevis : along each of the toes these tendons sub-divide at the joints between the first and second pha- 268 DUBLIN DISSECTOR. langes, into fasciculi, which pass over the sides of these articulations as the extensor tendons do on the fingers ; on the dorsum of the toes also they form a sort of aponeuro- sis as on the fingers, the tendons of the lumbricales and inter-ossei as also the tendons of the extensor brevis assist ing in its formation. 3. EXTENSOR POLLICIS PROPRIUS, arises tendinous and fleshy from the inner edge of the middle third of the fibula, and from the inter-osseous ligament nearly as low down as the ankle ; a few fibres also proceed from the lower part of the tibia ; the fibres descend obliquely forwards to a tendon, which passes beneath the annular ligament, then runs forwards over the astragalus, naviculare, and cunei- forme internum ; the tendon next passes over the first me- tatarsal bone, and is inserted by two tendinous fasciculi, one into the base of the first phalanx, and the other into the base of the second or last phalanx of the great toe. Use, to extend the great toe and flex the ankle ; it may also ad- duct the foot, and rotate it inwards. The upper and middle portions of this muscle are overlapped and concealed by the tibialis anticus and extensor cornmunis, between which muscles it is situated ; its tendon is superficial ; the ante- rior tibial nerve and vessels separate it from the tibialis anticus above, and from the extensor communis below ; it lies on the fibula and inter-osseous ligament above : infe- riorly it crosses over the tibial vessels, the synovial mem- brane of the ankle joint, and the bones of the tarsus. 4. PERON^EUS TERTIUS, or anticus, appears to be a portion of the extensor communis, and in some cases cannot be separated from it; it arises from the anterior surface of the lower half of the fibula ; the fibres pass forwards to a tendon which descends along with that of the extensor communis beneath the annular ligament ; it then passes forwards and outwards, and is inserted broad and thin into the base of the fifth metatarsal bone, and it frequently sends a band of fibres to join the fourth tendon of the ex- tensor eommunis. Use, to extend the little toe, to flex the ankle, to abduct the foot and raise its outer edge. This muscle is sometimes wanting, an additional tendon from the extensor communis will then supply its place ; it is su- perficial ; on the foot it conceals the extensor ibrevis, which may be next examined. EXTENSOR DIGITORUM BREVIS, is the only muscle situated on the upper surface of the foot, it arises tendinous and fleshy from the upper and anterior part of the os calcis, anterior to the groove for the peronseus longus, also from the cuboid bone, the astragalus, and the annular ligament ; it forms a flat fleshy belly, which passes forwards aad in- DUBLIN DISSECTOR. 269 wards, ends in four flat tendons, of which the two internal are the strongest ; the little toe does not receive any ; these tendons are inserted thus: the first or most internal, into the base of the first phalanx of the great toe ; the three other tendons join the outer edge of the corresponding tendons of the extensor digitorum longus, and assist in forming the aponeurosis which covers the dorsum of each toe. Use, to extend the toes and rotate the anterior part of the foot outwards. This muscle is partly concealed by the tendons of the long extensor and -peronseus tertius ; it pro- jects, however, behind and between them ; the tendons cross the metatarsal bones and the inter-ossei muscles, be- neath and in a contrary direction to the -long extensor ten- dons. There is no analogous muscle to this on the dorsum of the hand. [Varieties. The inner part is sometimes distinct from the rest, and sometimes the muscle presents four distinct bellies, as in birds. A tendon is sometimes sent to the little toe.] The muscles on the outer part of the leg are the two pe- ronaBi. 1. PERONJEUS LONGUS, arises tendinous and fleshy around the head of the fibula and from the adjacent surface of the tibia, from the upper half of the external angle of the fibula, from the fascia and inter-muscular septa, the fibres descend obliquely backwards and outwards, end in a strong, flat tendon, which passes behind the external mal- leolus, through a groove in the lower end of the fibula, in which it is bound down by a strong aponeurosis, lined by a synovia! membrane ; it then passes forwards, downwards, and inwards, through a similar groove in the os calcis and cuboid ; it next passes across the sole of the foot, above the plantar muscles, obliquely inwards and forwards towards the metatarsal bone of the great toe, into the outer side of which, and of the adjacent sesamoid bone, it is inserted; also, into the internal cuneiform, and into the base of the second metatarsal bone. Use, to extend the ankle joint, turn the foot outwards, and raise its outer edge, also to press the great toe against the ground as in walking ; in the leg this muscle is superficial, and is situated between the extensor communis anteriorly and the solceus and flexor pollicis posteriorly ; in the sole of the foot it is above all the muscles there, and cannot be seen until these are removed. 2. PERONJEUS BREVIS, arises fleshy from the outer and back part of the lower half of the fibula, and from the inter-mus- cular septa ; the fibres descend obliquely, end in a tendon which passes behind the external malleolua in the same 23* 270 DU'BLIN DISSECTOR, groove as the peronseus longus; it them passes forwards through a distinct groove in the s calcis above the pero- naeus longus, and is inserted into the base of the metatarsal bone of the little toe, and into the os cuboides. Use, simi- lar to the last. This muscle arises between the extensor longus and peronseus longus, and descends between the peronseus tertius and the flexor pollicis longus, and partly concealed by the peronseus longus; it continues fleshy lower down than it, and projects on either side of its ten- don ; it is separated from the peronceus tertius by the ex- ternal malleolus ; in the groove in the latter it is beneath the long peronceal tendon, that is nearer to the bone, but on the os calcis it is superior to it; an aponeursis some- times unites its insertion to that of the extensor tendon of the little toe, [Variety. This muscle is sometimes double.] In the dissection f the foregoing muscles we meet with the anterior tibial vessels and their branches; also the perongeal nerve and its divisions. The anterior tibial artery is a branch of the popliteal ; it passes forwards between the solceus and popMtasus, perforates the inter-osse@us space, surrounded by some fibres of the tibialis posticus ; it then descends obliquely inwards and forwards as far as the cleft between the first and second metatarsal bones ; ira its course down the leg it is placed at first between the tibialis anticus and extensor communis, in the middle of the leg between the former and the extensor pollicis, and inferierly between the tendon of the latter and that of the extensor 'communis ; above it lies on the inter-osseous membrane, below it passes over the tibia, the synovial membrane of the ankle joint, the. astragalus, navicular., and cuneiform bones, aiad beneath the annular ligament and the internal tendon of the exten- sor digitorum brevis ; in the leg the anterior tibial artery sends off, first, the recurrent branch, which ascends on the outer and fore part of the head of the tibia, and meets the external articular arteries; second, in its course along the leg, several muscular branches ; third, near the ankle, the two nanJiiealar branches, of these, the external is the larger, andinoscialates with a small artery (the anterior peronseal) which perforates the inter-osseous ligament about two inches above the ankle joint ; on the tarsus, the anterior tibia! artery sends off the tarsal and metatarsal branches, which pass obliquely outwards, arid supply the inter-ossei muscles, the bones and joints of the tarsus and metatarsus ; between the two first metatarsal bones the anterior tibial divides into the superior and inferior branch ; the former supplies the integuments of the great toe ; the latter passes 'DUBLIN DISSECTOR. 271 deep towards the sole of the foot, and fains the external plantar artery ; the anterior tibial artery is accompanied by two veins, which end in the popliteal vein. The pero- rucal nerve winds around the head of the fibula, perforates the peronee-us longus, and divides into several branches; some of these supply the perenseal muscles, others the in- teguments on the outer and fore part of the leg and -foot ; and the continuation of the peronreal nerve passes obliquely forwards and downwards, and accompanies the anterior tibial artery, lying in general superficial, and to its fibular side. EUSSECTION OF THE MUSCLES ON THE BACK F THE LEG. THESE muscles are seven in number, and may be divided into a superficial :and a deep layer ; the former consists of three, the gastrocnemius, solseus, and plantaris ; the latter of four, the tibialis posticus, flexor pollicis longus, flexor digitorum communis, and popliteeus. The cutaneous nerves and veins, and the fascia, have been already noticed. [Variety. The tendinous connection with the flexor communis is often wanting.] 1. GASTROCNEMIUS, large and thick, tendinous below, fleshy and aponeurotic above, and divided into two heads, both of which are somewhat oval, convex behind, flat be- fore ; the internal longer and larger than the. external; arises from the upper and back part of the internal condyle of the femur., and fleshy from the oblique ridge above it ; the external head arises in the same manner, from above the external condyle, but is not so long or large ; the fibres of each descend converging, and form two fleshy bellies, which unite a little below the knee in a middle tendinous line ; about the middle of the leg the muscle ends in a broad and flat tendon, which gradually unites with that of the solseus, and both form that strong tendon which is com- monly called the tendo AchilUs, and which is inserted, into the lower and back part of the os calcis. Use, to extend the ankle joint, and thus, by raising the heel from the ground, to throw the weight of the whole body forwards on the toes as in progression ; to flex the knee joint, also to secure the articulation against displacement, by preventing the condyles of the femur slipping 'backwards oft' those of the tibia. This large muscle is superficial, a small portion of its internal head is overlapped by the semi-membranosus; its deep surface is more aponeurotic than its superficial ; the lower angle of the popliteal space separates its two heads; in this angle the popliteal vessels, the posterior tibial nerve, and the plantaris muscle are contained ; a 272 DUBLIN DISSECTOR. foursa is placed between each head of this muscle and the condyle of the femur, which it covers ; the external head conceals the tendon of the poplitseus ; the internal covers the deep processes of the semi-membranosus tendon and an intervening bursa, also the insertion of the poplitasus ; the gastrocnemius covers the greater part of the solreus, therefore, to examine the latter, detach the heads of the gastrocnemius from the condyles, and separate this muscle from the solseus to within two or three inches of the heel ; the plantaris muscle is now also exposed. [This muscle is said to be the one most frequently affected with fatty transformation. I have a specimen in which, one lateral half of the muscle was entirely changed, while the other half appeared quite natural. The soleus also is often affected at the same time.] 2. PLANTARIS, arises fleshy from the back part of the femur above the external condylc, and from the posterior ligament of the -knee ; it is connected to the external head of the gastrocnemius, and forms a small pyramidal fleshy belly, which descends obliquely inwards, crosses the popli- teal vessels, and ends in a flat tendon (the longest in the body) which descends between the gastrocnemius and solseus ; and when the tendons of these muscles are about to unite, that of the plantaris becomes superficial, it then descends along the inner side of the tendo Achillis to the heel, and is inserted into the posterior part of the os calcis, a little anterior to the tendo Achillis : it has also some con- nexion to the plantar fascia. Z7se, to extend the foot, and turn it inwards, also to make tense the fascia, and to flex the knee; its origin is partly concealed by the external head of the gastrocnemius ; its tendon also is at first covered by this muscle, but inferiorly it is superficial. This mus- : cle is sometimes wanting. 3. SOLJEUS, of an oval flattened figure, consists superiorly of two heads, which are not so distinct from each other as those of the gastrocnemius; the external is longer and larger than the internal, and arises from the back part of the head and from the superior third of the fibula, behind the peronasus longus : the internal head arises from the middle third of the tibia, commencing below the oblique insertion of the poplitasus ; the two heads are connected by a strong tendinous arch, beneath which pass the poste- rior tibial nerve and vessels; all the fibres descend and form a large oval belly, which continues fleshy lower 'than the gastrocnemius; a tendon is formed first on its superfi- cial surface, which is gradually united to that of the gas- trocnemius to form the tendo Achillis ; this strong tendon is broad and thin above, narrow in the middle, and round and thick below, it is composed of strong vertical fibres DUBLIN DISSECTOR. 273 which descend behind the os calcis, over a bursa, covering a cartilaginous impression on that bone, and it is inserted into a rough surface below that. Use, to assist the gastroc- nemius in extending the ankle ; this muscle is almost en- tirely concealed by the gastrocnemius ; a little below the middle of the leg, however, it projects on each side of the tendon of the latter, and forms the lower calf of the leg ; it covers the deep seated muscles, vessels, and nerves. Detach the solaeus from its origin, and the strong deep fascia of the leg is exposed ; this fascia is partly derived from the semi-membranosus and poplitseus, and partly from the more superficial fascia of the leg ; it adheres to the ti- bia and fibula, to the solseus, and to the deep muscles ; in- feriorly this fascia is strong, and is connected to the sheaths of the tendons that pass behind the rnalleoli, and to the internal annular ligament of the ankle ; dissect off this fascia and clean the four following muscles. 4. PGPLITJTUS, situated obliquely at the upper and back part of the leg, behind the knee, and above the other mus- cles in this region, flat and triangular, arises by a round tendon from a depression on the external surface of the outer condyle, below the origin of the external lateral liga- ment, descends obliquely inwards and backwards, above the head of the fibula, and along the external semi-lunar cartilage, to which it is connected by the synovial mem- brane of the knee, and by a few tendinous fibres ; becomes broad and fleshy, and is inserted into a flat triangular sur- face, which occupies the superior fifth of the posterior sur- face of the tibia. Use, to bend the knee, and when bent, to twist the foot and toes inwards; it may also assist when the limb is extended in rotating the knee outwards : it sup- ports the external semi-lunar cartilage, and moves it slight- ly, so as to adapt its situation to the external condyle of the femur, in the rotatory motions of the joint ; the popli- tseus is covered by the two heads of the gastrocnemius and plantaris, also by the external lateral ligament, the popli- teal nerve and vessels ; it is superior to the inner head of the sola3us, and passes over the tibio-fibular articulation and the back part of the tibia ; it is nearly parallel to the up- per part of the plantaris ; the tendon is nearly surrounded by the synovial membrane of the knee, it lies however ex- ternal to' the cavity of the joint. 5. FLEXOR DIGITORUM PERFORATES, longus, or communis, broader in the centre than at either end, arises fleshy from the posterior flat surface of the tibia, commencing below the poplitseus, and extending to within two or three inches of the ankle, also from the fascia and inter-muscular sep- ta ; the fibres descend obliquely inwards to a tendon which 274 DUBLIN DISSECTOR. passes behind the internal malleolus, in a groove in the tibia which is lubricated by a bursa, and in which it is confined along with the tendon of the tibialis posticus by the internal annular ligament, separated, however, from that tendon by a ligamentous septum ; each tendon also has a distinct synovial sac : this tendon then turns forwards and a little outwards into the sole of the foot, still confined in a bony groove, first in the astragalus, and then in the os calcis ; in the sole of the foot it lies beneath the tendon of the flexor pollicis, and is connected to it by a tendinous slip; about the centre of this region it expands arid re- ceives the insertion of the accessory muscle, it then divides into four tendons, which pass to the four outer toes, and opposite the first phalanx, each tendon enters a strong fibrous sheath which is lined by synovial membrane ; this sheath continues as far as the extremity of the second pha- lanx, and contains also the corresponding tendon of the flexor digitorum brevis; opposite the base of the second phalanx, each of the last named tendons is slit for the trans- mission of the long flexor tendon, which continues to run forwards to be inserted into the last phalanx of each of the four lesser toes. Use, to flex the toes and the metatarsus, to extend the ankle, and to steady the leg on the foot as when standing. This muscle in the leg is covered by the superficial muscles, the deep fascia, and the tibial vessels ; it overlaps the tibialis posticus, and is on the inner or tibial side of the flexor pollicis ; a little above the inner ankle, the tendon of the tibialis posticus crosses above that of the flexor communis, that is, becomes nearer to the tibia ; in the sole of the foot its direction is horizontal, it is there su- perior to the flexor brevis, inferior to the transversalis pe- dis and peronseus longus tendon ; the lumbricales muscles arise from its tendons. 6. TIBIALIS POSTICUS, larger above than below, arises from the posterior and internal part of the fibula, from the up- per part of the tibia and from almost the entire length of the inter-osseous ligament ; the fibres descend and end in a strong tendon which passes along with that of the last muscle behind the internal ankle, crosses above that ten- don and then proceeds obliquely forwards and inwards, and is inserted into a tuberosity on the inferior and internal part of the os naviculare and into the internal cuneiform bone ; it also sends some fibres to the cuboid and to the second and third metatarsal bones ; a small bony or carti- laginous tubercle is often found in this tendon, near to its insertion, beneath the head of the astragalus; it also glides over a small bursa in this situation. Use, to extend the an- kle and 10 raise the inner edge of the foot from the ground ; DUBLIN DISSECTOR. 275 the upper end of this muscle is notched by the anterior ti- bial vessels, a few of its fibres accompany these vessels through the inter-osseous space and are attached to the an- terior surface of the ligament ; in its course down the leg it is covered by the soteus and overlapped by the flexor communis and flexor pollicis, it covers the tibia, fibula and inter-osseous ligament ; it passes beneath the head of the astragalus and supports that strong fibro-cartilage, which extends from the os calcis to the os naviculare, beneath the head of the astragalus, which substance supports a great portion of the weight of the body in standing or in progression. 7. FLEXOR POLLICIS LONGUS, arises from the two inferior thirds of the fibula by fleshy fibres which descend oblique- ly inwards to a tendon which passes behind the internal malleolus through a groove first in the tibia and next in the astragalus ; entering the sole of the foot this tendon crosses above the flexor communis and is connected to it by a tendinous slip, it then proceeds forwards and inwards, between the two portions of the flexor pollicis brevis, en- ters a tendinous sheath, and is inserted into the last phalanx of the great toe. Use, to flex this toe, to extend the ankle and adduct the foot ; this muscle lies to the fibular side of the tibialis posticus, between it and the peroneei muscles ; as it passes behind the internal ankle it is about half an inch, behind the tendons of the tibialis posticus and the flexor communis, and is separated from these by the poste- rior tibial nerve and vessels. SECTION V. DISSECTION OF THE MUSCLES OF THE FOOT. THERE is but one muscle on the dorsum or on the upper surface of the foot, the extensor digitorum brevis, which has been already examined, as being a sort of appendix to, or continuation of the long extensors of the toes which arise from the bones of the leg. The integuments and fas- cia in the sole of the foot have been already noticed ; the muscles here are very numerous, they may be divided into four lamina?, these are tolerably distinct about the middle of this region, but at either side this arrangement is rather artificial ; the two inter-muscular processes of the plantar fascia also divide these muscles into three compartments, an internal, a middle, and an external. The muscles of 276 DUBLIN DISSECTOR. the first, or superficial layer, are the abductor pollicis, flexor digitorum brevis, and abductor minimi digiti : in the second layer are the long flexor tendons, the accessory muscle, and the lumbricales : the third layer consists of the flexor pollicis brevis, adductor pollicis, transversalis pedis, and flexor minimi digiti ; in the fourth layer, are the inter ossei muscles, and the tendon of the peronseus longus. ABDUCTOR POLLICIS, arises tendinous and fleshy from the lower and inner part of the os calcis, from the internal an- nular ligament, the plantar aponeurosis, and internal in- ter-muscular septum; the fibres pass forwards and in wards, and are inserted tendinous into the internal sesamoid bone, and into the internal side of the base of the first phalanx of the great toe. Use, to separate the great toe from the others ; this muscle is by some writers called the adductor pollicis, its action being then referred to the mesial line of the body ; it is the most internal of the plantar muscles, and is superficial, the fascia covering it is very thin. FLEXOR DIGITORIUM BREVIS PERFORATUS, arises from the inferior and rather from the internal part of the os calcis, from the internal annular ligament, the plantar aponeuro sis, and inter-muscular septa ; it forms a fleshy mass, which passing forwards divides about the middle of the foot into four delicate tendons, which accompany the flexor longus communis into the tendinous and synovial sheaths, beneath the phalanges of the four outer toes ; each tendon is, slit opposite the base of the second phalanx, and having trans- mitted the long flexor tendon, this short tendon is then fold- ed out on the inferior surface of the second phalanx, and is inserted into it, above the long flexor tendon. Use, to as- sist the long flexor, to strengthen the plantar fascia, and to preserve the arch of the foot ; this muscle is immediately above the strong central portion of the plantar fascia, from which a considerable portion of it arises, therefore it always presents a rough surface, when dissected ; it is beneath the long flexor tendons, the accessory muscle, and the lumbri- cales ; it is joined to the abductor pollicis posteriorly, but anteriorly is separated from it by the tendon of the flexor pollicis longus : the fourth or the external of its tendons, or that for the little toe, is sometimes wanting. ABDUCTOR MINIMI DIGITI, is situated along the outer edge of the foot, arises tendinous and fleshy from the outer side of the os calcis, and from a strong ligament which ex- tends from this to the fifth metatarsal bone, also from the base of the latter, from the plantar fascia and its external inter-muscular septum ; inserted tendinous into the outer side of the base of the first phalanx of the little too, and into the adjoining surface of the metatarsal bone. Use, to DUBLIN DISSECTOR. 277 separate the little toe from the others, .and to flex it ; this muscle is also superficial, the fascia covering it is very strong, it is the most external of the muscles in this region, Detach this first layer of muscles from their posterior attachments, and throw them forwards towards the toes ; the tendons of the flexor pollicis and communis are now exposed, also the accessory muscle and the lumbricales ; all these constitute the second layer of the plantar muscles, which is partially concealed by the first. The tendon of the flexor longus digitorum communis is seen passing from the inner side of the os calcis to the middle of the plantar region, where it divides into its four tendons, which have been already described as entering the sheaths on the inferior surface of the four outer toes, pass- ing through the slits in the tendons of the flexor brevis, and then inserted into the last phalanx of each toe. The tendon of the flexor pollicis longus is now also seen pass- ing above the former, to which it is united by a tendinous fasciculus, and then proceeding forwards to its insertion in the base of the great toe. MUSCULUS ACCESSORIUS, or flexor digitorum accessorius, arises fleshy and tendinous, from the inferior and internal part of the os calcis, forms a flat and somewhat square fleshy belly, which proceeding forwards, is inserted into the upper and outer part of the tendon of the flexor digitorum longus, just before it divides. Use, to assist the long flexor, and to counteract its obliquity by pulling it directly towards the heel; this muscle lies above the flexor digitorum brevis. There is no analogous muscle to this in the hand, as there the flexor tendons pass directly over the centre of the carpus. LUMBRICALES are four small muscles which arise tendi- nous and fleshy from the tendons of the flexor digitoruro longus ; there is none for the great toe ; the first or the in- ternal one is the largest ; these four muscles proceed for- wards along the internal edge of the long flexor tendons, each ends in a thin aponeurosis, which is inserted into the internal side of the first phalanx of the four lesser toes, and joins the tendinous expansion of the extensor tendons on the dorsum of the toes. Use, to adduct and to assist in flex- ing the four toes, they may also extend their second and last phalanges. These muscles are covered in the sole ot the foot by the superficial layer ; their tendinous insertions are superficial, and are best seen on the dorsum of the toes. These are analogous to the four lumbricales in the hand, where they arise also from the deep or perforating flexors, and run along the radial side of each tendon, or that next the thumb, so in the foot they run along that side which 278 DUBLIN DISSECTOR. corresponds to the great toe ; hence, although they are de- scribed as running along the outer sides of the flexor ten- dons in the hand, and along the inner in the foot, yet still they are perfectly analogous, supposing the hand in the prone position, or the foot in the supine. Detach this se- cond layer of muscles and throw it also forwards towards the toes. The third layer of the plantar muscles consists of the flexor pollicis brevis, adductor pollicis, transversalis pedis, and flexor minimi digiti. FLEXOR POLLICIS BREVIS, narrow posteriorly, broad and notched anteriorly ; arises by a strong tendon from the lower and anterior part of the os calcis, also from the ex- ternal cuneiform bone, it forms a fleshy belly which is inse- parably connected to the abductor and adductor pollicis, and passes forwards and inwards, and divides into two short tendons ; these are inserted into the sesamoid bones beneath the first phalanx of the great toe. Use, to flex the first joint of the great toe, also to approximate this toe to the others. This muscle forms a sort of sheath for the ten- don of the flexor pollicis longus, and is analogous to the short flexor on the thumb. ADDUCTOR POLLICIS, is situated external to the last muscle, or more in the centre of the foot ; it is also inseparably at- tached to it ; it arises tendinous and fleshy from the strong calcaneo-cuboid ligament, and from the base of the second and third metatarsal bones, it passes forwards and inwards, and is inserted along with the external portion of the last muscle into the external sesamoid bone. Use, to draw the great toe outwards towards the other toes, also to flex it, so as to bring the great toe beneath the other toes. By some this muscle is named the abductor pollicis, its action being then referred to the mesial line. TRANSVERSALIS PEDIS, arises by distinct fleshy slips from the anterior extremities of the four external metatarsal bones ; the fibres pass inwards and forwards, converging to the external sesamoid bone of the great toe, into which they are inserted along with the last described muscle. Use, to approximate the toes, and to contract the transverse arch of the foot ; there is no analogous muscle in the hand ; be- hind this muscle, and nearly parallel to it, the strong cal- caneo-cuboid ligament is observed, also the tendon of the tibialis posticus dividing into several slips, which are in- serted into the adjacent bones and ligaments. FLEXOR BREVIS MIN.MI DIGITI, arises tendinous and fleshy from the cuboid and fifth metatarsal bone, and from the sheath of the peroneeus longus tendon ; it passes forwards and outwards, and is inserted into the inner side of the base DUBLIN DISSECTOR. 279 of the first phalanx of the little toe. Use, to flex and ad- duct this toe. This muscle is connected to the abductor minimi digiti ; it fills up the concavity of the fifth metatar- sal bone. Detach these four muscles in this layer from the tarsus, and the fourth layer will come into view, namely, the tendon of the peronseus longus and the interossei mus- cles ; the former crosses the foot obliquely forwards and inwards from a deep groove in the cuboid, beneath the cu- neiform and metatarsal bones, to be inserted into the inter- nal cuneiform, and into the base of the first and second metatarsal bones ; in this course this strong round tendon is enclosed in a tendinous sheath, which is lined by syno- vial membrane, and is attached to the several projections of the adjoining bones. Use, to serve as a strong trans- verse ligament in strengthening the tarsus and metatarsus in that direction ; this course and connexion of the tendon explain the action of the personseus longus muscle, namely, to extend the ankle joint, to elevate the external side of the foot, to depress its internal side, and to turn the point of the foot outwards. INTEROSSEI MUSCLES are seven in number; three are seen in the sole of the foot, and four on the dorsum ; they fill up the interstices between the metatarsal bones : the three in- ferior are named interossei interni or inferiores ; they arise tendinous and fleshy from between the metatarsal bones of the four external toes, and are inserted tendinous into the inner side of the base of the first phalanx of the three les- ser toes. Use, to adduct the toes. The first of the inferior interossei is situated between the second and third metatarsal bones, it arises chiefly from the inner side of the latter, and is inserted into the inner side of the first phalanx of the third or middle toe ; this may be named the adductor medii digiti ; the second is between the third and fourth metatarsal bones ; arises chiefly from the inner side of the latter, aud is inserted into the inner side of the first phalanx of the fourth toe, and may be named ad- ductor quarti digiti ; the third is between the fourth and fifth metatarsal bones, arises from the latter, and is inserted into the inner side of the little toe, and may be named the ad- ductor minimi digiti. The interossei externi or superiores are four in number, are larger than the last, and are seen on the dorsum or convex surface of the foot ; they are bicipital muscles ; the first is between the first and second metatarsal bones, and may be named the adductor digiti secundi ; it arises from the internal side of the second metatarsal bone, and by a distinct fas- ciculus from the outer side of the first ; these two origins are separated by the deep branch of the anterior tibial ar- 280 DUBLIN DISSECTOR. tery ; the fibres end in a tendon which is inserted on the in- ner side of the base of the first phalanx of the second toe ; it also joins the corresponding extensor tendon. Use, to ap- proximate the second to the great toe. ABDUCTOR DIGITI SECUNDI is placed between the second and third metatarsal bones ; arises from their opposite sur- faces, but chiefly from that of the former ; the fibres end in a tendon which is inserted into the outer side of the first phalanx of the second toe. Use, to separate the second from the great toe, ABDUCTOR DIGITI MEDII is placed between the third and fourth metatarsal bones, and arises from their opposite sur- faces, but chiefly from that of the third; the fibres end in a tendon which is inserted into the outer side of the first phalanx of the third or middle toe. Use, to separate the third toe from the first and second. ABDUCTOR DIGITI QUARTI is situated between the fourth and fifth metatarsal bones ; it arises from their opposite sur- faces, and is inserted into the outer side of the first phalanx of the fourth toe. Use, to separate the fourth toe from the three internal. All the interossei muscles serve to strengthen the meta- tarsus, to press the metatarsal bones together ; they also serve to flex the first joint of the four outer toes, and may assist in extending their last phalanges ; these muscles can exert no influence on the great toe ; there is only one mus- cle between the two first metatarsal bones; between the others there are two, therefore there are four superior or dorsal interossei muscles, but three inferior ; the latter are situated more in the concavity of each metatarsal bone than between these bones ; the superior are stronger and more tendinous than the inferior ; and are only partially covered by the long and short extensor tendons. In dissecting the muscles on the back of the leg, and those in the sole of the foot, we meet the posterior tibial vessels and nerve, and their principal branches. The posterior tibial artery is the larger branch of the popliteal ; it descends obliquely inwards beneath the deep fascia and the superfi- cial muscles, and over the tibialis posticus and flexor com- munis, to the fossa between the heel and inner ankle, it here ends in the two plantar arteries ; in this course it gives off many muscular branches, also the peron&al artery; the latter arises from the tibial, about an inch below the poplitseus ; it descends obliquely outwards along the back part of the fibula beneath the flexor pollicis longus ; be- hind and a little above the outer ankle, it divides into the anterior and posterior peroneeal arteries ; the former per- forates the interosseous space and joins the external mal- DUBLIN DISSECTOR. 281 leolar artery; the latter descends between the external ankle and the heel, and is distributed to the ligaments and adipose substance in that region. The two plantar branches of the posterior tibial artery are distributed to the muscles and integuments of the foot and toes ; the internal plantar is the smaller of the two, it supplies the muscles along the inner side of the tarsus ; the external plantar, the larger branch, runs across the foot obliquely outwards, towards the fifth metatarsal bone, be- tween the first and second layers of the plantar muscles ; from the little toe it next runs obliquely forwards and in- wards, towards the first metatarsal bone, above the second layer of the plantar muscles, and between the first and second metatarsal bones it joins the deep branch of the anterior tibial artery, and thus forms the great plantar arch of arteries, from the convexity of which proceed the digital arteries, to supply the toes, (see Anatomy of the Vascular System.) The posterior tibial artery and its several branch- es are accompanied by corresponding veins, all of which end in the popliteal vein. The posterior tibial nerve is the principal branch of the sciatic, it accompanies the poste- rior tibial artery, at first lying to its tibial, afterwards to its fibular side ; in this course it sends off several small branch- es to the deep and superficial muscles of the leg, and be- tween the heel and ankle it divides into the two plantar nerves, which take the course of the corresponding arte- ries. In this internal malleolar region, when the integu- ments, fascia and internal annular ligament are removed, we find the three tendons and the posterior tibial nerves and vessels to have the following relation to each other, the tibialis posticus and flexor communis tendons are bound close to the ankle, about half an inch behind these is the posterior tibial artery accompanied by two veins, the nerve is a little nearer to the heel, and the tendon of the flexor pollicis lies about half an inch nearer to the latter. 24* PART II. CHAPTER I. ANATOMY OF THE NERVOUS SYSTEM. THIS SYSTEM MAY BE DIVIDED INTO FOUR PRINCIPAL PARTS, THE BRAIN, THE SPINAL CORD, THE NERVES AND THE GANGLIONS. SECTION I. DISSECTION OF THE BRAIN. THE brain is subdivided into three portions, cerebrum, cerebellum, and 'medulla oblongata; these are, however, so intimately connected, that it is difficult to mark the exact limits of each. Divide the scalp from one ear across the vertex to the other; reflect one flap over the face, the other over the back of the neck ; make a circular cut with the saw through the cranium on a level with the cartilage of the ear on each side, anteriorly about an inch above the superciliary arches, and posteriorly a little below the tubercle of the os occipitis. It is only necessary to saw through the outer table of the bones, the elevator, or a few smart strokes with the claw of the hammer will then suffice to crack the internal table; (indeed the cranium may be opened by the hammer alone, this plan however injures the bones so much as to leave them of little use to the student) The calvarium being now forcibly torn away, the dura mater is exposed ; the latter, in some subjects, adheres so closely to the bone as to be torn along with it ; this a-ccident will injure the brain, and may be avoided by introducing the handle of the knife or any blunt instrument between the membrane and the bone as you gradually raise off the latter. If the student can procure two subjects it will facilitate his study to ex- DUBLIN DISSECTOR. 283 amine the brain of both at the same time ; in one dissect the parts in situ, and from the other remove the brain in the following manner : commencing anteriorly, gently raise it from the base of the skull, divide each nerve and vessel in succession from before backwards close to the bone, dis- locate the pituitary gland from the sella turcica, and cut through the tentorium ; next divide the spinal cord as low down in the neck as you can pass the knife through the foramen magnum ; then place the brain, its base upwards, in a shallow basin ; thus the different surfaces and struc- tures of the brain, as also the several processes and sin- uses of the dura mater, can be examined in continuation with each other. The MEMBRANES covering the brain are three, the dura mater, arachnoid membrane, and pia mater ; the first may be termed the fibrous, the second the serous, and the third the vascular coat ; these tunics also extend through the spi- nal canal and cover the spinal cord. The dura mater is a fibro-serous membrane, of very con- siderable strength and of a whitish colowr, sometimes it has a bluish tint ; the external surface adheres intimately to the bones; it now presents a rough surface and several red spots, particularly in the course of the sutures ; these are owing to the ruptured vessels which passed from the dura mater to the bone, the former being the internal periosteum to the latter; in the young subject the connexion between the two is so close and vascular, that it is very difficult to separate them in the recent state, and when this is effected numerous bioody dots are observable on each ; this mem- brane is more intimately attached to the bones at the base of the cranium than in any other situation, it there sends small processes through the several foramina, some of these accompany the vessels and nerves, and are gradually lost on them, others become continuous with the periosteum ; the most remarkable of these processes, next to that which is continued along the spinal canal, is one which passes through the foramen lacerum orbitale, and joins the peri osteum in the orbit, and another which surrounds the optic nerve and is united to the sclerotic coat of the eye. Several small arteries ramify on this membrane, between it and the bones of the cranium, anteriorly these are derived from the ophthalmic and internal carotid vessels ; the middle artery of the dura mater is the largest, this is a branch of the in- ternal maxillary, it enters the base of the cranium through the spinous hole in the sphenoid bone, passes forwards and upwards above the temporal and sphenoid bones, then as- cends obliquely backwards on the inner surface of the parietal bone, the anterior and inferior angle of which it 284 DUBLIN DISSECTOR. grooves very deeply ; posteriorly the dura mater receives several small arteries, viz. branches from the occipital, pharyngeal and vertebral arteries; these vessels of the dura mater also supply the superincumbent bones with blood. Cut through this membrane parallel to the edge of the cranium, raise it from each side of the brain towards the vertex, leaving a small portion of it in the mesial line both before and behind undivided; the internal surface is now seen to be smooth and polished, and moistened with a fine serous exhalation ; this surface is the reflected or the parietal layer of the arachnoid membrane, (to be examin- ed presently,) it adheres so closely to the dura mater that it is difficult to separate them for any extent, unless previ- ously macerated. From the internal surface of the dura mater folds or pro- cesses extend into the cranium, which divide this cavity in- to several compartments and support and separate different portions of the brain ; these processes are the falx cerebri tentorium cerebelli and falx cerebelli. The falx cerebri is exposed by gently separating one hemisphere of the brain from the other ; it commences narrow at the crista galli and the middle ridge of the ethmoid bone, thence it ascends in the median line, and passing backwards, ends by being continued into the tentorium ; the convex edge of this pro- cess corresponds to the middle ridge or groove of the os frontis, to the sagittal edge of the two parietal bones, and to the perpendicular ridge of the occipital ; the great lon- gitudinal sinus is enclosed between the layers of this pro- cess, the whole extent of this edge ; the concave or inferior border of the falx corresponds to the middle line of the corpus callosum, from which it is but a very short dis- tance ; the inferior or lesser longitudinal sinus is enclosed in this edge ; the falx divides the cavity of the cranium in the median line, it separates the hemispheres of the cere- brum, and in different positions of the body supports the weight of each ; in old subjects it is often cribriform, and in some it is partly converted into bone. [I have a specimen of ossification of the falx cerebri taken from a subject, that died of apoplexy.] The tentorium cerebelli extends in somewhat a horizontal direction across the posterior part of the cranium; it may be seen by gently raising the back part of either hemis- phere of the brain ; the convex edge of this fold is attach- ed to the transverse ridge of the occipital bone, to the in- ferior angle of the parietal bones, to the superior angle of the petrous bones, and to the posterior clinoid processes of the sphenoid ; over this last attachment, the concave edge DUBLIN DISSECTOR. 285 of the tentorium glides and is inserted into the anterior cli- noid processes ; the tentorium is raised and held in a state of tension along the median line by the falx, its inferior surface is concave ; anteriorly it presents a large oval opening, which is on a plane anterior to the foramen mag- num, this is filled by the superior vermiform process of the cerebellum, the crura cerebri, and the pons varolii ; along the convex edge of the tentorium, between its layers, are two sinuses on each side, the great lateral and the superior petrous; in the median line also is another called the straight sinus, which extends along the base of the falx ; the tentorium serves to support the weight of the cerebrum off the cerebellum. The falx cerebelli is seen when the brain is removed ; it is a small but thick process of little importance, the base is superiorly attached to the tentorium, the apex inferiorly, at the foramen magnum : its convex edge adheres to the oc- cipital spine, and contains between its layers the occipital sinuses ; its concave edge separates the hemispheres of the cerebellum ; this process serves to retain the tentorium and falx cerebri in a state of tension. Attached to the lesser wing of the sphenoid bone, on each side, is a slight fold of dura mater, termed the sphenoidal fold ; these serve to in- crease the surface of the anterior fossse of the base of the cranium, and correspond to the fissures of Sylvius at the base of the brain. The uses of the dura mater are, first, to serve as a periosteum ; second, to cover the brain ; third, by its processes to separate and support the different parts of this organ ; fourth, to form sheaths for several of the nerves as they leave the cranium ; and fifth, to form the sinuses which may be next examined. The sinuses correspond to the veins, or in fact they are veins enclosed between the laminse of the dura mater, which thus retain them in their situation, and enable them to resist distention; the principal sinuses are sixteen in number, viz. the superior and inferior longitudinal, the straight, the right and left lateral, the superior and inferior petrous, the right and left cavernous, the circular, the trans- verse, the occipital, and the torcular Herophili. The supe- rior longitudinal sinus commences at the crista galli, either in a small cul de sac, or by a small vein from the nose ; it extends upwards and backwards along the median line, in- creasing in size, and opposite the tubercle of the os occipi- tis it divides into the right and left lateral sinuses, the right branch being in general the larger; with the scissors lay open this sinus through its whole length ; it appears some- what triangular, lined by a smooth fine membrane, which is continuous with that lining the venous system ; in gene- 286 DUBLIN DISSECTOR. ral it is usually dilated near the vertex ; small white fibrous bands cross it in many places ; these have an imperfect re- semblance to the valves of veins ; and may serve to resist distention of the sinus : they have been named corda Wil- lisii; about the middle of this sinus there are in general a number of small whitish bodies, sometimes lying singly, but more frequently in clusters, near the openings of some of the veins in the sinus, these are termed glandultz Pac- chioni; their size, number, and appearance, diifer consider- ably in different subjects ; in the very young there are few, if any ; in the old, they are most numerous, and often so very large, as to cause considerable depressions in the frontal and parietal bones ; they are found in three situa- tions, in the cavity of the sinus, external to the dura mater, or internal to it ; the first are termed the glandulae mediae, the second, the external, and the third the internae ; their use or structure is unknown, most probably they are by no means allied to the glandular system. The longitudinal sinus, like all the other sinuses, consists of two tunics, the internal or the venous membrane, and the external or fibrous coat derived from the dura mater ; this membrane is described as dividing into two layers on either side of the cavity ; one continues to adhere to the bone, and the other laminae descend on either side of the sinus, and unite in the falx ; the base of the triangular cavity thus formed is towards the bone, the apex towards the falx ; in addition to many small veins, from the bones and from the dura mater, this sinus receives near the vertex eight or ten large veins from the upper surface of each hemisphere of the brain, these run obliquely forwards between the coats of the sinus, some for an inch, others for less, before they open into the cavity, and just as they are terminating, they turn slightly, so that their mouths look inwards, or towards those of the opposite side ; all the veins which enter the sinus do not take the oblique course now described, and which is most probably designed to impede the reflux of the blood from the sinus into the cerebral veins. The in- ferior longitudinal sinus is not always present, it resembles a small vein enclosed in the lower edge of the falx near its base, it receives small veins from the corpus callosum, and ends in the following; the straight sinus, is situated in the median line, enclosed between the laminae of the base of the falx and above the tentorium, it receives the blood from the lateral ventricles returned by the two venae Galeni ; this sinus proceeds backwards, and downwards and ends in the confluence of the two lateral and longitudinal sinuses; it presents internally the same fibrous appearance as the great longitudinal sinus. The lateral are the largest sinuses. DUBLIN DISSECTOR. 287 of somewhat an elliptical figure, each proceeds at first hori- zontally outwards and forwards, enclosed between the lami- na? of the tentorium, in a groove in the occipital bone, and in the inferior angle of the parietal ; it then descends inwards along the mastoid portion of the temporal bone, and again indenting the occipital, it turns forwards, and passing through the foramen lacerum posterius, ends in the inter- nal jugular vein. [It occasionally happens that both lateral sinuses, do not follow the course here described, but that one of them descends along the falx. cerebelli, nearly to the foramen magnum, of the os occipitis, and then diverges so as to reach the foramen lacerum posterius, being situated upon the occipiial bone through its entire course. I have a specimen of this kind on the right side, and Meckel states that this anomaly is generally found on the right side.] Each lateral sinus receives several small veins from the posterior lobes of the cerebrum and from the cerebellum ; these enter the sinus from without inwards, contrary to the current in the sinus ; through these sinuses all the blood is returned from the cranium to the general system ; there are seldom any transverse bands or glandule Pacchioni in these sinuses. The following sinuses are situated on the base of the cranium. The cavernous sinus on each side ex- tends from the anterior clinoid process to the point of the petrous bone along the side of the body of the sphenoid ; the dura mater in this region divides into two layers, one very thin adheres to the irregular bony surface which bounds this cavity, the other much more dense is reflected over this space, and contains between its laminse the third and fourth nerve, and the first part of the fifth : the oph- thalmic vein which has passed through the foramen lace- rum orbitale superius, opens into the fore part of this sinus, and the two petrpsal sinuses lead from it posteriorly to the lateral sinus ; this sinus is intersected by tendinous bands, and presents rather a cellular or spongy appearance like the corpus cavemosum penis ; the internal carotid artery and the sixth or abducens nerve pass through the cavity of this sinus, also several small branches from the sympa- thetic ; the venous membrane, however, is reflected around each, so as to separate them from the blood ; the cavernous sinuses communicate through the following; the circular sinus consists of two small veins, which lead from one cavernous sinus to the other, the anterior is beneath the optic commissure, and before the pituitary glands ; the pos- terior is behind and rather below that body. The petrosal sinuses are four in number, two on each side, the superior and inferior; they each lead from the cavernous sinuses backwards, the former along the upper edge of the petrous 288 DUBLIN DISSECTOR. bone, to the lateral sinuses opposite the inferior angle of the parietal bone ; the inferior petrous sinus leads down- wards and backwards, over the suture between the petrous and occipital bones, and ends in the lateral sinus near its termination. The transverse sinus leads from one inferior petrosal sinus to the other, across the cuneiform process of the occipital bone. The occipital sinuses are two small canals contained in the falx cerebelli ; they receive veins from the cerebellum, and sometimes from the vertebral canal, and open into the torcular Herophili ; these sinuses sometimes extend along each side of the foramen magnum, and communicate with the lateral sinuses; the occipital sinuses are often wanting. The torcular Herophili is a sort of common reservoir in which several sinuses end ; it is situated opposite the tuberosity of the occipital bone, and enclosed between the layers of the falx and tentorium ; it is somewhat oval, and presents six openings, viz. the late- ral sinus on each side, the longitudinal sinus above, the straight sinus before, and the occipital sinuses below. The second covering of the brain is a serous membrane, the arachnoid, so fine and delicate that in some situations it is difficult to demonstrate it ; between the convolutions of the brain it can be raised from the pia mater, which sinks into the fissures between these ; and a little air forced be- tween these membranes will separate them for some dis- tance, and will raise the arachnoid membrane in a vesicular form ; on the base of the brain, and in the spinal canal, it is stronger, and can be distinctly detached from the subja- cent membrane. The arachnoid membrane covers the whole surface of the brain, and is thence reflected to the dura mater, which it lines throughout, except at the sella turcica, where the pituitary gland intervenes between these membranes ; from the surface of the brain it is reflected on the dura mater in several situations, viz. superiorly, as the veins enter the longitudinal sinus, this membrane ac- companies them from the brain to the sinus, it is then reflected to the inner surface of the dura mater : inferiorly, also, it surrounds the nerves in their course from the brain to the foramina, through which they pass, and is then re- flected on the dura mater, the latter membrane being really perforated and continued for a short distance around each nerve, whereas the arachnoid membrane forms a cul de sac at the exit of each ; thus the arachnoid membrane, like all serous membranes, forms a shut sac, one side or layer of it (the parietal) adhering to the dura mater ; the other (the visceral) covering the brain and extending from one emi- nence to another, without penetrating between them ; it is smooth, polished and transparent, without any distinct DULLIN DISSECTOR. 289 vessels ; it exhales and again absorbs a fine serous halitus which allows the opposed surfaces to move against each other without friction ; this membrane is also continued into the cavities or ventricles of the brain, and gives to them a smooth lining. To see this process of the arach- noid membrane, separate gently the posterior lobes of the cerebrum, divide the falx, and at the 'anterior edge of the tentorium the two venee Galeni will be seen entering the straight sinus; these veins are surrounded by the serous membrane ; press these gently to one side, and underneath them a small round hole or canal may be observed, leading forwards below these veins, and above the pineal gland, and opening into the back part of the third ventricle ; this canal is lined by the arachnoid membrane, which is con- tinued from that on the surface of the brain, and expands within the ventricles, so as to cover all the inequalities ob served within them ; this arachnoid canal, or the canal of Bichat, will be noticed again in the examination of the ven- tricles. The third tunic of the brain is the vascular coat, or the pia mater, of a very soft and delicate structure, loaded with numerous fine vessels ; it adheres to the whole surface of the brain, and following every involution of its surface, it is intimately united with its substance by numerous shreds and vessels, wnich admit of being drawn out like fine threads ; on the convolutions of the brain it is insepa- rably connected to the arachnoid membrane, but in most other situations, particularly at the base of the brain, they are but loosely united to each other. The pia mater is also prolonged into the lateral ventricles, through an extensive fissure, which will be seen in the dissection of the brain between the fornix and the corpus callosum above, and the tubercula quadrigemina and pons Varolii below ; this fis- sure descends obliquely forwards on each side into the in- ferior cornu of each lateral ventricle between the optic thalamus and the hippocampus major; through these lateral prolongations of this fissure, a process of the pia mater enters, termed the choroid plexus, and through the central or transverse portion of it, another process, termed the choroid membrane or velum interpositum ; these pro- cesses are covered by the arachnoid membrane, and are all connected together, as will be seen in the dissection of the ventricles ; this great fissure in the brain is closed every where by the arachnoid membrane on the surface of the brain except at the foramen of Bichat. The use of the pia mater is to form an exact capsule for the brain, also an extensive surface, on which the vessels divide minutely, and are probably arranged in some peculiar manner, previous to their penetrating the substance of the brain. 290 DUBLIN DISSECTOR. There are two modes of dissecting the brain ; first, by removing it in successive slices from above down- wards ; and, secondly, from below upwards ; the first plan is best adapted for studying the relative anatomy of the different parts of the brain, or for examining this organ pathologically ; the second for unravelling its structure ; the student should practise both, and first, that from above downwards. DISSECTION OF THE CEREBRUM. [The great volume of the cerebrum seems to be characteristic of man ; there are certain inferior animals, in which the whole ence- phalic mass is proportionably greater than in the human race ; but this is not true of the cerebrum as considered by itself, it being pro- portionably greater in man than in other animals. This would cer- tainly seem to favor the phrenological philosophy, which locates the moral and intellectual faculties in the cerebrum, and the animal pro- pensities in the cerebellum. In the horse and the ox the weight of the cerebrum does not exceed half that of the human subject. The volume of the cerebrum is independent of stature, and of sex, although it was formerly thought to be smaller in the female than the male. Again its volame is proportionably greater in the foetus and infant than in the adult, and in old age it not unfrequently is atrophied to a certain extent. The weight of the cerebrum is from two to three pounds, averaging about two and a half, the cerebellum being equal to from a seventh, to a twelfth of the cerebrum. The an tero- poste- rior measurement of the cerebrum is about six inches, its greatest breadih which is behind, five inches, and its vertical diameter from four to five inches. It is said that the volume of the entire encephalo. rachidian mass, as compared with that of the nerves connected with it, is greater in man, than in any inferior animal.] THE CEREBRUM is the largest part of the brain, of an oval figure, the larger end posteriorly, a little flattened on the sides, convex above, and divided into two equal portions, the right and left hemispheres, by a deep fissure which ex- tends along the median line ; this fissure is continued be- fore and behind through the entire depth of the cerebrum, but in the middle it is bounded below by the corpus callo- sum ; it contains the falx cerebri and the arteries of the corpus callosum; each hemisphere is convex superiorly and externally, and flat internally, or towards the falx, in- inferiorly very irregular and uneVen ; the surface of each hemisphere is every where marked by a number of emi- nences termed the convolutions of the brain ; these are of various size and shape, and are somewhat convoluted like the intestines ; their round edges are separated by fissures which are closed by the arachnoid membrane ; these fis- sures are nearly an inch deep ; they take different direc- tions, serpentine, longitudinal, and oblique ; if a section of DUBLIN DISSECTOR. 291 the cerebrum be made, these fissures will be found to be only involutions of the cineritious substance covering the brain ; each fissure, therefore, is only a continuation of the surface, and is covered throughout by the pia mater. The cerebrum, on its inferior surface, is also divided into the two hemispheres by the great median fissure at each extremity, and in the centre by a depression containing several substances ; each hemisphere inferiorly is divided into three lobes, the anterior, small, triangular, flat, or a little concave, rests on the roof of the orbit, presents a deep groove which lodges the olfactory nerve ; the middle lobe is prominent, round, and deep, fills up the middle fos- sa in the base of the cranium, and is separated from the anterior lobe by a deep fissure, (Jissura Sylvii,') which as- cends obliquely outwards and backwards ; this fissure cor- responds to the sphenoidal fold of the dura mater, and to the lesser wing of the sphenoid bone ; the brain above it is perforated by a number of small holes for the entrance of vessels (pars perforee externe;) this fissure contains the middle artery of the brain, and one origin of the olfactory nerve. The posterior lobe rests on the tentorium, and is separated from the middle only by a slight excavation ; between the hemispheres we observe, immediately behind the anterior extremity of the median fissure, the lower end of the cor- pus callosum ; posterior to this, and connected to it is the commissure of the optic nerves ; behind this is a soft grey substance, the tuber cinereum ; this is connected anteriorly to these nerves, and posteriorly to two small white bodies termed the corpora mamiUaria or albicantia : these are about the size of small peas, situated behind the tuber cinereum, and attached by it to each other ; they are grey internally, although white externally, the anterior pillars of the fornix terminate in these. From the centre of the tuber cinereum a thin conical tube of a reddish colour descends, the infun- dibulum ; this passes behind and rather beneath the com- missure of the optic nerves ; it terminates on the surface of the pituitary gland ; it is surrounded by arachnoid mem- brane ; it is not pervious inferiorly ; above it communicates with the third ventricle. The pituitary body is placed in the sella Turcica between the dura mater and arachnoid membrane ; transversely oval, composed anteriorly of a yellowish substance, which is notched before, and convex behind like a kidney, and posteriorly of a whitish semi- fluid or pulpy substance. Behind the corpora albicantia, we next observe a small triangular depression, closed above by a thin plate which forms the posterior part of the floor of the third ventricle ; this is the middle perforated plate 292 DUBLIN DISSECTOR. of the brain ; on either side of this is the cms cerebri, con- necting the cerebrum to the pons Varolii, which last is situ- ated in the median line behind the last described substances ; behind the pons is the posterior extremity of the corpus callosum, and between these eminences is the great trans- verse fissure which transmits the pia mater into the ventri- cles, and which also contains the arachnoid canal and the pineal gland ; behind this we observe, lastly, the posterior extremity of the median fissure separating the posterior lobes of the cerebrum. Cut off the upper part of one hemisphere nearly on a level with the corpus callosum, the appearance now pre- sented is termed the centrum minus ovale, a mass of white substance surrounded by the irregularly undulating line of grey substance ; a small cavity or fissure may now also be observed between the corpus callosum and the lower and internal margin of each hemisphere : next slice off both hemispheres on a level with the corpus callosum, and the centrum magnum ovale is presented, that is, a line of grey substance surrounding the central mass of white substance. The grey or cortical or cineritious substance of the brain is soft and pulpy, and more vascular than the white ; on the surface of the cerebrum it is about the eighth of an inch in thickness ; in other situations it is placed in considerable masses, and covered by the white substance ; the shade of its colour differs in different parts of the brain, and in dif- ferent subjects : in the child it is reddish, in the old it is grey or ashy. It consists of a number of very minute glo- bules, connected together by the pia mater m and vessels. The white or medullary substance is more firm, and when fresh, has some elasticity, and in many parts appears dis- tinctly fibrous; its divided surface appears dotted with red spots ; these are the divided vessels, they vary in number and in size in different subjects : in a very fresh brain, when a section has been made of this white substance, it will, by its elasticity, force the blood to exude out for some little time in small drops from the divided vessels. The corpus callosum is now seen in the median line of the cere- brum, but nearer the frontal than the occipital bone, be- tween three or four inches long, convex, white, marked by two or three raised longitudinal lines close and nearly pa- rallel to each other, (the raphe^ from these several trans- verse lines [linea transverse] pass to either side ; its poste- rior end broad, round, and a little concave, is bent down- wards, and is continuous on either side with the fornix and the hippocampi ; its anterior end is also round, and bent downwards and backwards, is continued on each side into the anterior lobes, and in the middle it joins the tuber cine- DUBLIN DISSECTOR. 293 reum and the optic commissure ; the corpus callosum con- nects the white fibrous substance of the hemispheres, and is therefore properly called the great commissure of the cerebrum ; it covers the lateral ventricles, the septum luci- dum, and the fornix. Divide this substance at a little dis- tance from either side of the raphe, the lateral ventricles will be opened, press the middle portion of the corpus cal- losum to one side, and the septum lucidum may be seen descending in the median line from it to the upper surface of the fornix. The septum lucidum separates the two late- ral ventricles, and is triangular, the apex behind, the base before, the upper edge connected to the corpus callosum ; the lower edge to the fornix posteriorly, and anteriorly to the inferior curved portion of the corpus callosum ; it con- sists of four lamina?, two on each side, grey externally, white internally ; between the white laminae a small cavity exists termed the fifth ventricle. This cavity is naturally closed, but when the corpus callosum is divided trans- versely, and the anterior portion raised forwards, the la- minae of the septum separate, and this cavity becomes dis- tinct ; it i-s larger in the child, but it is very irregular in size, and even in existence, in different subjects ; the sep- tum lucidum appears to be formed by a lamina descending from each side of the raphe of the corpus callosum to the fornix, some grey matter superadded. Divide transversely the septum lucidum and corpus callosum, raise forwards the anterior portion of the latter, and backwards its poste- rior part ; it will now be seen that this substance is united to the fornix posteriorly, but is nearly an inch above it. an- teriorly ; the septum lucidum is generally so soft that in this stage of the dissection it will have nearly broke down into the surrounding fluid. The lateral ventricles extend from the middle of the brain into the anterior and posterior lobes, also to the inferior part of the middle lobe, hence they are named tricorne ; the anterior cornu of each passes forwards and outwards, they are about an inch distant from each other ; the middle por- tion, or the body of each, passes horizontally backwards, they are separated from each other by the septum luci- dum ; near the posterior part of the corpus callosum the posterior and inferior cornua pass off in different direc- tions; the posterior cornu proceeds into the posterior lobe al first outwards, afterwards it turns inwards in a curved direction, the concavity towards the median line ; the infe- rior cornu descends obliquely forwards and outwards into the middle lobe, and is then also curved a little inwards ; it terminates behind the fissure of Sylvius and beneath the anterior cornu. The anterior cornu is bounded superiorly 25* 294 DUBLIN DISSECTOR. and laterally by the corpus callosum, and inferiorly by the large extremity of the corpus striatum ; the middle, or body of each, is bounded superiorly and externally by the cor- pus callosum ; internally by the septum lucidum, and in- feriorly by the posterior extremity of the corpus striatum, the toenia semicircularis, the optic thalamus, the choroid plexus, and the fornix. The posterior cornu is bounded superiorly and laterally by the medullary substance, and inferiorly by the hippocampus minor. The inferior cornu is bounded superiorly by the optic thalamus, externally by medullary substance ; internally it is deficient of cerebral substance, and is closed by the arachnoid membrane ; infe- riorly by the hippocampus major and corpus finabriatum or tsenia hippocampi. The several bodies, observed in the different regions of these cavities, must next be examined individually ; and first, corpora striata. These pyriform bodies have their larger ends directed forwards and inwards ; their posterior small and pointed extremities pass backwards and out- wards ; smooth and unattached superiorly and internally, on all other sides they are continuous with the white sub- stance, vascular, soft, and cineritious on their surface ; they will be found, when cut into, to -consist of alternate laminae of grey and white substance; the latter may be traced from the crura cerebri through these bodies to the upper and anterior part of the cerebrum, hence the cor- pora striata are named by some the anterior or superior ganglions of the cerebrum. The tccnia semi-circularis, is a narrow, semitransparent band, whitish, fibrous, placed in the groove between the optic thalamus and corpus stria- tum ; it arises narrow from a tubercle on the back part of the optic thalamus, (corpus geniculatum externum,) passes forwards and inwards, becomes broader, and joins the de- scending pillar of the fornix; the anterior portion has a resemblance to the cornea, and has been named lamina cornea : several veins from the corpus striatum pass be- neath the tcenia to join the vense Galeni. The choroid plexus is a fold of thin vascular membrane derived from the pia mater; it enters the inferior cornu between the optic tha- lamus and the tcenia hippocampi; loose and floating it as- cends obliquely backwards over the hippocampus major, then turns forwards between the thalamus and the fornix, beneath which it is connected to the choroid membrane, and ends by uniting with its fellow in the foramen com- mune anterius ; each choroid plexus is covered by the arachnoid membrane ; they receive a number of veins from the parietes of the ventricles, particularly from the corpora striata ; these veins join the vence Galeni, which will be DUBLIN DISSECTOR. 295 noticed presently ; very frequently small vesicles, hydatids, and even small hard tumours may be found in these mem- branes. The fornix, white, fibrous, triangular, is situated horizon, tally, beneath the corpus callosum and septum lucidum attached to the former posteriorly, to the latter anteriorly it lies on the velum interpositum and choroid plexuses, the base, posteriorly, arises by two flat bands, (the posterior pillars or crura,) one from either side, by three roots, from the hippocampus major and minor, and from the tamia hip- pocampi ; these crura pass forwards and inwards, and unite (the body of the fornix ;) this bends forwards and down- wards, over the foramen -commune anterius, and divides into two short, round, white cords, (the anterior pillars of the fornix,( these descend behind the anterior commissure, and end in the corpora mamillaria, which are connected to the grey substance of the tuber cinereum ; the inferior surface of the fornix which rests on the velum is marked posterior- ly by several fine oblique lines (lyra or corpus psalloides.} Although the septum lucidum is a partition between the lateral ventricles, yet these cavities communicate together, as also with the third or middle ventricle, through an open- ing termed /oramen commune anterius ; this is situated in the median line at the anterior part of the body of each ven- tricle, it is bounded superiorly and anteriorly by the for- nix, posteriorly by the two choroid plexuses and velum, laterally it leads from one lateral ventricle to the other, and inferiorly it opens into the third. The optic thalami cannot be fully examined at present. In the posterior cor- nu of each ventricle is a small eminence, the hippocampus minor, large anteriorly, small and pointed behind, white on the surface, grey internally. In the inferior cornu we see the hippocampus major, a large white substance, convex ex- ternally, concave internally, smooth and white on the sur- face, grey within, extending all along the floor of the cavi- ty, and ending in a tuberculated expansion, the pes hippo- campi; along its internal or concave edge, and connected to it, is a narrow white band, the t&nia hippocampi or cor- pus fimbriatum, the concave edge of which is loose ; this substance is directly continuous with the posterior pillar of the fornix; beneath the tasnia hippocampi, a narrow ci- neritious line may be observed, shorter than the tainia, its edge is serrated ; this is the corpus denticulatum. Divide the fornix about its centre, draw forwards its anterior portion, and the foramen commune anterius will be seen ; throw the posterior portion backwards, and the choroid membrane or the velum interpositum will be exposed ; this is of a trian- gular form, beneath the fornix, and above the arachnoid 296 DUBLIN DISSECTOR. canal, the optic thalami, the pineal gland, and the third ven- tricle ; the choroid plexuses are united to it laterally and in front, the verm Galeni extend along its median line ; these veins receive the blood from each plexus, and from the dif- ferent eminences in the ventricles, they pass backwards, and end in the straight sinus, they sometimes first unite in- to one trunk ; the velum is formed of pia mater, which is continued from the surface of the brain through the great transverse fissure, which is beneath the corpus callosum and the fornix, and above the tubercula quadrigemina and the pineal gland ; it is also covered by the arachnoid mem- brane, which is of extreme delicacy ; raise this membrane from before backwards, first dividing the small veins which run into it, the optic thalami will be now exposed, and pos- terior to these the pineal gland, and the superior surface of the tubercula quadrigemina ; the anterior extremity of the arachnoid canal also is seen ; this orifice is beneath the veins of Galen and above the gland ; it is in general sur- rounded by small granulations ; remove the velum. The pineal gland is situated above the tubercula quadrigemina, behind and between the thalami, about the size of a pea, cineritious, heart-shaped, the base anteriorly containing, in general, some small sandy particles (the acervulus,) the pos- terior part is soft and pulpy, (the conarium) is surrounded by a very vascular membrane derived from the velum; unconnected to the brain in every situation, except ante- riorly, whence a small transverse medullary band proceeds, which divides into two long delicate processes, (pedunculi,) these pass forwards on the inner surface of the optic thala- mi, and join the descending pillars of the fornix, at the fo- ramen commune anterius. The optic thalami, two firm bo- dies white on their surface, grey within, placed behind and between the corpora striata, smooth superiorly where they enter into the lateral ventricles, touching each other inter- nally, where they are soft and grey ; this connexion is termed the commissura mollis, it is a broad, soft, and cineri- tious union between the internal surfaces of the thalami, and anterior to their centre, this must be broken through before the third ventricle can be seen ; a sort of fissure se- parates the thalami ; this fissure anteriorly leads to the fo- ramen commune anterius, and posteriorly to the foramen commune posterius, this last hole is behind the soft commis- sure, and between the peduncles of the pineal gland, it is, however, so closed by the velum and the forndx. that no communication can occur through it between the third and the two lateral ventricles, as through the anterior common opening; the optic thalami externally and anteriorly are continuous with the corpora stiata and the medullary sub- DUBLIN DISSECTOR. 297 stance of the hemispheres ; inferiorly they present two tu- bercles ; (corpus geniculatum internum and externum;") their an- terior extremity is in the foramen commune anterius, their posterior is in contact with the corpus fimbriatum ; the up- per surface of each is in the body of the lateral ventricle, the inferior surface is in the inferior cornu ; through the sub- stance of the thalami some portious of the crura cerebri pass in their course to the convolutions of the hemispheres, hence they are named by some the inferior ganglions of the brain. Separate the optic thalami, and the third or middle ventricle will be opened. The third ventricle is a narrow cavity placed in the median line, bounded on each side by the optic thalami, above by the velum and the for- nix, below by the locus perforatus arid tuber cinereum, be- fore by the descending pillars of the fornix and the ante- rior commissure, behind by the posterior commissure and pineal gland, its peduncuH and the tubercula quadrigemi- na. The foramen commune anterius opens into the upper and anterior part of this cavity ; the infundibulum leads from the lower and anterior part downwards and forwards, between the pillars of the fornix and below the anterior commissure, to the pituitary gland; this canal is large above, but it is generally impervious below. From the pos- terior part of the third ventricle a small canal leads back- wards and downwards, above and behind the pons Varolii, and below the tubercula quadrigemina, this is the aqueduct of Sylvius or the iter ad quartum ventriculum. The anterior commissure is a distinct round cord, extending from one he- misphere to the other, immediately before the anterior pil- lars of the fornix, bent like an arch, convex anteriorly, unattached in its central portion, but on each side it is im- bedded in the corpus striaturn, through which it descends obliquely backwards and outwards, and then terminates in rays near the fissure of Sylvius, and the inferior cornu of the lateral ventricle ; it is enclosed in a delicate sheath of pia mater, like a nerve. The posterior commissure is shorter and smaller than the anterior, but white, round, and fibrous like it ; it extends transversely behind the third ventricle, above the aqueduct of Sylvius, below the pedunculi of the pineal gland to which it is connected, and anterior to the tubercula quadrigemina ; its extremities are connected, to the optic thalami. The tubercula quadrigemina are below and behind this commissure and the pineal gland, they are all connected by their bases, on an oblique plane, and se- parated from each other near their points by two superfi- cial grooves, a transverse and a vertical ; the two superior and anterior are called the nates, the two inferior and pos- terior the testes, white on their surface, grey internally ; 298 DUBLIN DISSECTOR. they lie above and behind the aqueduct of Sylvius, which alone separates them from the pons Varolii ; the nates are connected to the optic thalami, and the testes to the cere- bellum, by two thin white plates, which descend oblique- ly backwards and outwards, and end in the substance of the cerebellum ; these are the processus a cerebello ad testes ; they diverge towards the cerebellum, and are continuous externally and interiorly with a thick, round, white chord, the crus cerebelli ; between these two processes there is a thin lamina extended named the valve of Vieussens, or of the fourth ventricle, cineritious and very soft, triangular, the apex between the testes, the base attached to the cerebel- lum, and the sides to the two processes just described ; this valve forms the roof of the fourth ventricle, it is overlapped by the superior vermiform process. Pass a probe along the aqueduct of Sylvius, divide the valve of Vieussens, and the cavity of the fourth ventricle will be exposed ; this is directed obliquely downwards and backwards, between the cerebrum, cerebellum, and medulla oblongata ; it is bound- ed anteriorly by the pons Varolii, in the median line of which is a narrow fissure, the calamus scriptorius, from each side of which a few white lines pass off to join the auditory nerve ; laterally by the processes from the testes and by the crura cerebelli ; superiorly by the valve of Vieussens ; posteriorly -by the cerebellum, and inferiorly by the reflec- tion of the arachnoid membrane, and of the pia mater from the inferior surface of the cerebellum to the back of the spinal cord ; the pia mater is here peculiarly dense, and it sends a small process into the lower part of this cavity, (the choroid plexus of the fourth ventricle,) which is loaded with tortuous vessels, and frequently presents a small num- ber of reddish granular bodies. Raise either hemisphere of the cerebrum ; from its infe- rior surface, just below the corpus striatum and the optic thalamus, a thick, white fasciculus may be observed de- scending obliquely backwards and inwards; this is the crus cerebri; fibrous and white on the surface, each crus in- ternally contains cineritious substance of a very dark co- lour (locus niger ;) the crura cerebri converge as they de- scend, and end in the upper extremity of the pons Varolii ; the third ventricle is between them, and the tractus opti- cus of each side surrounds them. The crura cerebri and the following substance can be better examined when the brain is removed from the subject, and the base placed up- permost. The pons VaroJii or cerebral protuberance is somewhat square, it is placed obliquely on the cuneiform process, between the cerebrum and cerebellum ; the fourth ventricle, the aqueduct of Sylvius and the tubercula qua- DUBLIN DISSECTOR. 299 drigemina, are on its superior and posterior surface ; its inferior and anterior surface rests on the bone, and is grooved longitudinally by the basiiar artery ; its superior extremity receives the crura cerebri, which it surrounds like a ring, hence it is sometimes called the annular protu- berance ; the crura cerebelli are attached to its sides, and the medulla oblongata to its lower extremity, from which it is distinguished by a deep groove: the pons is of a more firm structure than any part of the brain, its surface is white and fibrous ; the superficial layer of fibres on its in- ferior surface runs transversely from one crus cerebelli to the other, hence the pons has been named the commissure of the cerebellum ; beneath this lamina of transverse fibres a quantity of cineritious substance exists, through which white fibrous substance may be seen to ascend obliquely outwards, in the direction of the crura cerebri. The pons Varolii is described by some authors as a portion of the medulla oblongata ; it is, however, so connected with it as well as with the cerebrum arid cerebellum, that it may be considered as equally common to all. DISSECTION OF THE CEREBELLUM. [The average weight of the cerebellum is six ounces, its transverse diameter averages from three and a half to four inches, its antero-pos- terior diameter from two, lo two and a half inches, and its vertical diameter also from two, to two and a half inches. These measure, ments being made at its broadest, longest, and thickest parts. The average proportion of the cerebellum to the cerebrum, is as one to seven. The volume of the cerebellum, is greater in man than in all other animals. According to Gall and Cuvier, it is proportionably greater in woman, than in man, while it is proportionably less in the child, than in the adult. It is also said by Gall to be in proportion to the generative function, this however, Cruveilhier considers mere hy- pothesis, because certain species of animals remarkable for their vene- real ardor have the cerebellum very small, and because the inverte- brated animals have no cerebellum. The cerebellum is continuous, on the one hand, superiorly with the cerebrum through the processus a cerebello ad testes ; on the other hand, with the medulla oblongata through the corpora restiformia, or processus a cerebello ad medullam oblongatam. Again a continuity between the two hemispheres of the cerebellum, is established! by transverse fibres, in the annular pro- tuberance. In four cases Cruveilhier has seen atrophy of the right hemisphere of the cerebrum, and of the lel'l hemisphere of the cere- bellum conjoined. The cerebellum does not become distinct until after the medulla spinalis, and the medulla oblongata, and in the earliest months of utero- gestation passes through stages of develop- ment, which resemble the cerebellum of fish and of reptiles.] REMOVE the posterior lobes of the cerebrum, divide the tentorium, and the cerebellum will be exposed ; transverse- 300 DUBLIN DISSECTOR. ly oval, raised in the centre, divided into right and left he- mispheres by a deep groove posteriorly and inferiorly, which receives the falx cerebelli, and by a broad notch anterior- ly which is behind the fourth ventricle ; the upper surface of each hemisphere is nearly flat, and is marked by a great number of narrow lines which run semicircularly, convex posteriorly ; these are fissures into which the pia mater de- scends, the arachnoid membrane passing over them ; these fissures are analogous to those in the cerebrum ; they are involutions of the grey substance, the superficial extent of which is thus considerably augmented : the same appear- ance is also observable inferiorly ; the lines, however, are not so numerous or regular as above ; some lines pass in very deep into the cerebellum, and divide it into lobes, others are only superficial : and divide it into lobules ; the inferior surface of each hemisphere is very convex, and fills the inferior occipital fossse. Along the circumference of each hemisphere a deep fissure extends, at the bottom of which a white cord is observed ; this is the cms cerebetti, which ascends obliquely forwards and inwards to join the pons Varolii ; this great fissure separates the superior from the inferior surface. The central portion of the cerebel- lum is narrow, and raised superiorly into a small conical process, the superior vermiform process, this overlaps the valve of Vieussens, the tubercula quadrigemina, and the processus a cerebello ad testes ; inferiorly there is a deep depression, which contains, anteriorly, the commencement of the spinal cord, and posteriorly a large process, the infe- rior vermiform which is marked by numerous transverse lines or fissures, which divide it into several laminse or lo- bules. Divide either hemisphere parallel to, and about an inch from the median line, a thick mass of white substance is seen in the centre, branching out into fine fibres, which extend into the lobes, and again subdivide into fine fila- ments, which pass to every lamina or lobule on the surface, and are there covered by a thin layer of grey substance ; [this arrangement is called the arbor vitae,] nearly in the centre of this white mass, which is continuous superiorly with the processus ad testem, and inferiorly with the crus cerebelli, is a small oval mass of grey substance, its edges convoluted or serrated ; this is the corpus dentatum or rhom- boideum ; the white substance which is continued from the medulla oblongata to the crus cerebelli, appears to run through this, and thus to be increased in quantity : hence it is named by some the ganglion of the cerebellum. DUBLIN DISSECTOR. 301 DISSECTION OF THE MEDULLA OBLONGATA. [The medulla oblongata is situated so as to extend from the upper margin of the first cervical vertebra, to the middle of the basilar fossa of the occiput. Its extent superiorly and anteriorly, is defined by the annular protuberance, not so posteriorly. Inferiorly it gradu- ally diminishes in circumference, and is continuous with the medulla spinalis, it is however, limited here artificially, and is said to be from an inch, to one inch and a quarter in length ; this however will de- pend somewhat upon the position of the head, its breadth is eight or nine lines at its base and its thickness six lines.] THE medulla oblongata is that conical portion of white substance which extends from the lower margin of the pons Varolii to the spinal cord, about an inch in length, large above, narrow below, where it passes through the foramen magnum, divided by longitudinal lines into six oval eminences placed parallel to each other ; the median line anteriorly separates the two corpora pyramidalia; next to each of these is a slight groove, external to which is the corpus olivare, behind which is a groove and another eminence, the corpus restiforme or the posterior pyramid. The corpora pyramidalia are about an inch long. [They extend the whole length of the medulla oblongata, being a line and a half in breadth below, but gradually increasing until they acquire a breadth of three lines above.] And they arise gradually from the fore part of the spinal cord above the atlas, ascend parallel to each other, increase in size, enter the pons, and they may be traced through this substance for some extent ; the median fissure, which extends along the spinal cord, separates them ; near the pons this fissure enlarges into a small hole (foramen cae- cum.) Dissect off the pia mater from these eminences, en- deavour to separate them from each other, and about three quarters of an inch below the pons five or six white bands may be observed ascending obliquely from one corpus py- ramidale to the other, the fasciculi of opposite sides per- fectly indigitating with each other ; these are the decussat- ing fibres of the pyramids. The corpora olivaria are oval, large in the centre, white on the surface, and containing within a corpus fimbriatum of grey substance; they are separated by a superficial groove from the former eminences ; their upper extremity is continued into the pons Varolii. [From which they may be traced into the thalami nervorum opti- corum. They are but six or seven lines long, and two and a half lines broad, and are elevated about a line. Internally they are sepa- rated from the pyramids, by a slight fissure, in which are the roots of the hypoglossal nerve, and externally there is a deep fissure, be. 26 302 DUBLIN DISSECTOR. tween these, and the corpora restiformia. The corpora olivaria are almost peculiar to man, they are found in other mammalia, but are small and do not exist in birds, reptiles, and fish.] The corpora restiformia are rather larger than the last, be- hind which they are placed ; they are separated from each other by a fissure which is continued from the calamus scriptorius along the posterior median line of the spinal cord; the restiform bodies are continued superiorly into the crura cerebelli, hence they are sometimes named the processus a medulla spinali ad cerebellum : they are also partly continued into the crura cerebri. [They are continuous with the posterior fissure of the medulla spinalis, and on the upper surface of the medulla oblongata, is a re- markable excavation, between the corpora restiformia, the calamus scriptorius which is marked by medullary strise, which give origin to the auditory nerve, and some of which Meckel, supposes to be con- nected with the trifacial and pneumo-gastric nerves.] ORIGIN OF THE CEKEBRAL NERVES. THERE are nine pair of cerebral nerves ; their connexion to the brain is named their origin ; they are distinguished by the terms first, second, third, &c., &c. ; in every respect, those of the opposite side are symmetrical. The FIRST PAIR, or OLFACTORY, are situated beneath the anterior lobes of the brain ; each arises by three filaments, the external, very long and white, from the fissure of Syl- vius, below the corpus striatum ; the internal, also white, from the grey substance at the extremity of the corpus cai- losum ; the middle is cineritious, and arises from one of the posterior convolutions of the anterior lobe; the three fila- ments soon unite and form a triangular swelling, from which the nerve proceeds forwards and inwards for about two inches, in a groove in the anterior lobe, in which it is confined by the arachnoid membrane and protected from pressure ; it then ends in a soft oval bulb which is placed over the cribriform plate of the ethmoid bone ; from this several fine filaments descend through the foramina in this bone, and are distributed to the mucous membrane in the nose. The olfactory differ from the other cerebral nerves in figure, course, and structure ; prismatic or triangular, the apex is imbedded in the cerebrum ; they converge as they leave the cranium; they consist of several striae, some white, others grey, all very soft : they are not surrounded by arachnoid membrane, but lie above it ; they have no distinct sheath, and each ends in a soft grey swelling from which the ultimate filaments proceed, and which leave the cranium by a number of foramina. The SECOND PAIR, or OPTIC, are large, soft, and flat poste- DUBLIN DISSECTOR. 303 riorly, round and inclosed in a dense neurilema anterior- ly ; each arises by two bands, one from the nates, the other from the testis ; these pass outwards beneath the optic tha- lamus, the first joins the corpus geniculatum externum ; the second the corpus geniculatum internum ; these roots then unite in a soft flat band, which turns forwards in a semicircular course (tractus options) around the crus cere- bri, to which it has a slight attachment, and from which it receives a few fibres : the optic nerves then converge, and unite before the sella turcica, in the optic commissure ; in this flat, white, square substance, which is connected to and receives additional fibres from the tuber cinereum, the two nerves are so confounded that the direction of each is indistinct, and it is uncertain whether they decussate in whole or in part ; from the commissure each nerve passes forwards and outwards on the inner side of the carotid and above the ophthalmic artery, through the optic foramen, into the orbit ; it is then surrounded by a process of dura mater, and proceeding to the back part of the eye, it perfo- rates the sclerotic and choroid coats of this organ, and ter- minates in the retina. The THIRD, or MOTORES OCULORUM, are smaller than the optic ; each arises from the inner side of the crus cerebri, close to the pons, behind the floor of the third ventricle, and between the posterior artery of the cerebrum, and the anterior artery of the cerebellum ; this round nerve passes forwards and outwards external to the cavernous sinus, through the foramen lacerum orbitale, and is distributed to five of the seven muscles contained in the orbit. The FOURTH, or TROCHLEATORES, or PATHETICI, are the smallest of the cerebral nerves ; each arises by two or three delicate filaments from the valve of Vieussens and from the processus a cerebello ad testem ; it takes a long course forwards and outwards between the cerebrum and cerebel- lum, enters a small canal between the layers of the tento- rium behind the posterior ciinoid process, and continues its course along the outer side of the cavernous sinus through the foramen lacerum orbitale to the superior ob- lique muscle. The FIFTH, or TRIFACIAL, or TRIGEMINI, are the largest of the cerebral nerves ; each consists of nearly one hundred fine filaments, but loosely connected to each other, and very easily detached from the brain : arises by two fasci- culi, one, large and posterior, from the angle between the pons Varolii and the crus cerebelli, the other, small and anterior, from the corpus pyramidale in the substance of the pons ; these pass together forwards and outwards over the point of the petrous bone in a sort of canal formed of 304 DUBLIN DISSECTOR. dura mater, and lined by arachnoid membrane, which last is reflected on the nerve, so as to form a cul de sac around it ; in the middle fossa of the base of the cranium it ex- pands into a large grey swelling, (the triangular, semilunar, or Casserian ganglion;} this ganglion is concave posteriorly ; convex anteriorly and externally ; the dura mater covers and adheres intimately to its plexiform surface ; three large branches proceed from it, the ophthalmic, the superior and inferior maxillary ; the first passes into the orbit through the foramen lacerum ; the second leaves the cranium by the foramen rotundum, and the third by the foramen ovale. If the ganglion be raised from the bone, a small fasciculus of fibres may be observed to pass from the trunk of the fifth pair, without entering into the ganglion, to the inferior maxillary nerve ; this fasciculus can be traced into the an- terior root of the fifth, or through the pons Varolii into the corpus pyramidale. When this nerve is detached from the brain, a small nipple-like tubercle is seen on the latter at the point of separation. The fifth pair of nerves resemble the spinal nerves, in arising by two roots, and in having a ganglion placed on the posterior, to which the anterior is only connected. The SIXTH, or ABDUCENTES, are of a middle size between the third and fourth ; each arises from the outer side of the corpus pyramidale, a little below the pons, it passes for- wards and outwards, pierces the dura mater behind the body of the sphenoid bone, traverses the cavernous sinus on the outer side of the carotid artery, and is there joined by two or three small filaments from the superior cervical ganglion of the sympathetic nerve, it then enters the orbit through the foramen lacerum, and is distributed to the ex- ternal rectus muscle ; the basilar artery is between the sixth pair of nerves. The SEVENTH PAIR consists of two portions, the PORTIO DURA, or the FACIAL nerve, and the PORTIO MOLLI-S, or the AUDITORY nerve. The facial nerve is the anterior and smaller of the two, it arises from the lower edge of the side of the pons below the crus cerebelli, and behind and above the corpus olivare. The auditory nerve, or portio mollis, is the posterior and the larger, it arises by three or four strise from the side of the calamus scriptorius and from a small mass of grey sub- stance on the back cf the corpus restiforme ; these are at first separated by the restiforme, but soon unite into one soft white cord, which passes forwards and outwards and joins the portio dura ; the two nerves then pass outwards, the mollis being larger than the dura, which is contained in a groove in the former, and a small blood vessel runs DUBLIN DISSECTOR. 305 between them ; they both enter the meatus auditorius in- ternus, where they soon separate ; the facial nerve runs along the aqueduct of Fallopius, which canal opens infe- riorly at the stylo-mastoid foramen ; this nerve then turns forwards, and is distributed to the side of the face ; the auditory nerve descends obliquely forwards, and is distri- buted to the cochlea and semicircular canals. The EIGHTH PAIR, or PAR VAGUM, consists of three por- tions, the GLOSSO-PHARYNGEAL the smallest, the PNEUMO- GASTRIC the largest, and the SPINAL ACCESSORY, which is of a medium size. The glosso-pharyngeal arises by four or five delicate fila- ments between the corpus olivare and restiforme; these unite into one small nerve. The pneumo-gastric, or the vagus, arises by ten or twelve filaments below the last, but in the same groove ; these also unite into one nerve, which, with the glosso-pharyn- geal, passes forwards and outwards to the foramen lace- rum posterius or jugulare, where they are joined by the third portion. The spinal accessory nerve arises from the side of the me- dulla spinalis by several delicate roots or fibres, which commence a little above the middle of the cervical portion of this organ. (Sometimes these roots commence as far down as opposite the seventh cervical nerve ; there are also three or four filaments from the medulla oblongata.] This nerve ascends behind the ligamentum denticulatum, and very near the posterior roots of the spinal nerves ; it frequently receives filaments from the roots of these nerves : having passed through the foramen magnum it joins the other divisions of the eighth pair, the inferior artery of the cerebellum having previously passed between them. The eighth pair of nerves passes through the jugular foramen anterior to the vein and immediately separates into its three portions, the particular course of each of which shall be considered afterwards. The spinal accessory is distributed to the muscles on the side of the neck ; the glosso-pharyn- geal to the pharynx and the tongue, and the pueumo-gas- tric to the lungs and stomach. The NINTH or LINGUAL nerve arises by six or eight fine filaments between the corpus olivare and pyramidale, and behind the vertebral artery; these unite and pass through the lingual or anterior condyloid hole in the occipital bone. The ninth pair of nerves are distributed to some of the in- ferior muscles of the neck, also to those of the tongue. Nerves are either simple or compound ; by simple is meant 26* 306 DUBLIN DISSECTOR, a nerve possessed of but one property ; by compound, a nerve possessed of two properties. The properties with which nerves are endowed, so far as we are positively in- formed, are two, viz. sensation and volition ; nerves endowed with the former are called sensitive nerves, the latter are the voluntary nerves or nerves of motion. Of the nine pair of cere- bral nerves some are simple, some compound, the simple are the first, second, third, fourth, sixth, and ninth ; the first and second are simple nerves of sense ; the third, fourth, sixth and ninth, are simple nerves of motion. The fifth, seventh, and most probably the eighth, are all compound nerves, thus the ganglionic portions of the fifth are sensi- tive, while the non-ganglionic are motor ; the portio mollis of the seventh is sensitive, but the portio dura is motor. The peculiar position of the origin of the eighth from the side of the medulla oblongata and spinal cord would imply that it partook of the double properties of these organs, that is, of their anterior and posterior surface, and that it was a compound nerve, and accordingly, in experiments on living and on recently killed animals, irritation applied to the divisions of the eighth pair, has in the former state of the animal produced pain, and in the latter muscular contraction. [The cranial or cerebral nerves, are so called because they pass out of the foramina, of the cranium, and not as the name would imply be- cause they all arise from the cerebrum, for we have just seen that many of them arise from the medulla oblongata, and in one case even from the medulla spinalis low down. The nine pair of nerves, above described are named by Willis and others indifferently, according to to their origin, from before backwards, numerically, or according to their distribution and uses. There is however a defect in the above arrangement, for we find that the seventh pair as described, includes two nerves entirely distinct in their distribution and uses : again the eighth pair comprehends three distinct nerves, accordingly Soemmer- ing modified the nomenclature as follows. First pair, Olfactory nerves. Second pair, Optic nerves. Third pair, Motores Communes Oculorum. Fourth pair, Trochleatores, or Pathetici Fifth pair, Trigemini, or Trifacial. Sixth pair, Abducentes, or Motores Externi. Seventh pair Portio Dura, or Facial nerve. Eighth pair, Portio Mollis, or Auditory nerve, Ninth pair, Glosso-Pharyngeal. Tenth pair, Par Vagum, or Pneumo Gastric. Eleventh pair, Spinal Accessory. Twelfth pair, Sublingual, or Hypoglossal. This appears to be much the best arrangement, except that the spinal accessory nerve should be considered as the twelfth pair, in DUBLIN DISSECTOR. 307 consequence of its arising low down from the medulla oblongata, and medulla spinalis. In accordance with the present state of our knowledge of the de- velopment of the nervous system, as regards priority, we ought to examine the cranial nerves from behind forwards, instead of from be- fore backwards, and in this more philosophic point of view the spinal accessory, would be the first pair. The present more common mode of examining them is, however, the most convenient.] Before the student dissects the cerebral nerves to their termination, he may examine the spinal marrow, and also dissect the brain from below upwards. CHAPTER II DISSECTION OF THE MEDULLA SPINALIS. THE spinal marrow is contained or rather suspended in a cavity or canal much larger than itself, and which is bounded by the bodies and processes of the vertebrae and by their connecting ligaments ; this organ, like the brain, is surrounded by three membranes, which are continuous with those in the cranium. Place the subject on the fore part, remove the soft parts covering the spine, and with the saw divide the crura of the spinous processes of all the ver- tebras close to their articulating processes, then with the elevator raise the posterior arch of the spinal canal; a quantity of loose reddish cellular tissue, and the numerous vertebral venous sinuses, intervene between the bones and the dura mater, which membrane is loosely connected to them, and cannot therefore serve the office of periosteum as in the cranium ; it is more closely attached to the liga- ments and bones anteriorly, than laterally or posteriorly. The dura mater of the spinal canal is termed the theca vertebralis ; it is continued from the cranium through the foramen magnum, down the spinal canal as far as the third lumbar vertebra, where it divides into several processes, which are continued on the sacral nerves ; throughout this extent it regularly sends off a tubular process along each of the spinal nerves ; its external surface is smooth and polished. With the scissors divide this membrane along its whole length ; its internal surface will be found lined by the reflected layer of the arachnoid or serous membrane. The arachnoid or the serous membrane in this region has a corresponding appearance to that in the cranium; it is. 308 DUBLIN DISSECTOR. however, rather stronger, and more loosely connected to the pia mater, so that air or any fine fluid may be impelled between them ; a quantity of serous fluid is also naturally interposed, so that this, unlike other serous membranes, must possess two exhalant and absorbent surfaces. From the sides of the spinal marrow it is regularly reflected along each of the nerves of the dura rnater ; these several reflections or folds, when examined in succession, are found to be continuous with each other, and assist in forming the following substance, the ligamentum denticulatum ; this is a narrow membranous and ligamentous band extending along each side of the whole spinal cord ; its superior extremity is attached to the dura mater at the foramen magnum ; its internal edge is straight, and is connected to the pia mater along the side of the spinal cord in the space between the anterior and posterior roots of the spinal nerves ; its exter- nal edge is serrated and attached by several pointed pro- cesses to the inner surface of the dura mater, near the fora- mina for the passage of the nerves ; each of these processes lies between the anterior and posterior fasciculi of the nerves ; its inferior extremity is inserted into the ligamen- tous substance on the body of the fourth or fifth lumbar vertebra. The ligamentum denticulatum serves to separate the roots of the spinal nerves, also to connect or fix the spinal cord laterally, and so guard against concussion or displacement of the cord. The pia mater in the spinal canal is more dense than in the cranium, it adheres so closely to the spinal cord as to appear to compress it, which is evident when the cord is cut across ; it is not so uniformly vascular as it. is on the brain, very large and tortuous vessels however extend along its whole length. The MEDULLA SPINALIS extends from the foramen mag- num, where it is continuous with the medulla oblongata as far as the second lumbar vertebra, where it ends in a lash of nerves called cauda equina ; this organ is almost cylin- drical ; its transverse diameter exceeds the aotero-poste- rior ; a deep narrow fissure extends along the median line posteriorly, and a broad superficial groove anteriorly ; at first the medulla spinalis is rather contracted or smaller than the medulla oblongata ; but from the fourth or fifth cervical to the first dorsal vertebra it is larger than in any other situation ; it then contracts through the upper ana 1 middle dorsal regions, and again swells out about the tenth dorsal vertebra into an oval bulbous expansion which ter- minates at the second lumbar vertebra in a point, from which the remains of the ligamenta dentata extend ; this lower extremity of the spinal cord is sometimes round, DUBLIN DISSECTOR. 309 sometimes bifid. The two enlargements of the spinal cord correspond to the origins of the largest nerves, viz. those to supply the upper and the lower extremity. The medulla spinalis appears to consist of two symmetrical portions united at the bottom of the two fissures by transverse bands or commissures, [Which are three in number, anterior, posterior and middle. Be- sides these commissures, there is a distinct decussation of the anterior columns, for the space of four or five lines near the occipital foramen, a. fact of much pathological value.] If either side be divided by a transverse section, it will be found to consist of grey and white substance, the latter placed externally, the former internally, and of a lunated appearance, the concavity looking outwards ; some grey substance is also placed transversely, and connects the convexities of these lateral masses. The younger the sub- ject the more distinct is the cineritious substance in the spinal cord. The medullary substance on each side ap- pears to be arranged in three columns, separated by super- ficial grooves : from these the spinal nerves proceed, and it has been ascertained by Majendie and Bell, that the pos- terior roots of these nerves are endowed with sensation only, and that, the anterior are connected with voluntary motion ; Bell also intimates, but without sufficient proof, that the middle, or those which arise from the sides of the cord, preside over the function of respiration. [There is a remarkable difference in the relative situation of the medulla spinalis, as placed in the vertebrated and invertebrated ani- mals. In the former it is superior, or posterior to the alimentary canal, in the latter it is inferior. In length the medulla spinalis mea- sures from fifteen to twenty inches, according to the stature of the individual ; its breadth, where most contracted is about one inch, and at its widest parts one inch and a half. Its length also depends somewhat upon the position of the subject, for it is elongated during the flexion of the spine, arid retracts again during extension ; this variation is estimated by Cruveilhier, at from twelve to fifteen lines. Neither does the medulla fill the whole circumference of the canal, but there is a space between the arachnoid tunic, and the dura mater filled by the cerebro- spinal fluid, this arrangement protects the medulla from compression, during the varied movements of the spine. The medulla spinalis is usually described, as ending opposite the first or second lumbar vertebra, but it sometimes descends as low as the third, and has been seen, to end opposite the eleventh dorsal vertebra. Thus we find that its length is not proportioned to that of the spinal canal; in the earlier months of foetal life,the medulla extends down to the sacrum. In vertebrated animate the volume of the medulla spinalis as compared with the size of the animal, is in direct ratio with its vital activity, hence it is small in fish and reptiles, large in birds and mammalia. According to Soemruering, its volume in man, 310 DUBLIN DISSECTOR. relatively to the encephalon, is smaller than in other animals, but in proportion to the size of his body, man has a larger medulla than any other animal except birds. Chaussier says that the volume of the medulla, is equal to from a nineteenth to a twenty-fifth part of that of the cerebrum, in the adult, but that in the new born infant it is but one fortieth. The volume of the spinal marrow at particular points, is in proportion to the size and number of the nerves connected with it, and the energy of function, in those organs, to which these nerves are distributed ; and the func- tion of sensation is connected with nerves of greater size than those connected with muscular contraction. We find that the cervical en- largement of the spinal marrow, is greater than the lumbar, for two reasons, the one because the superior extremity possesses a greater extent and variety of motion than the inferior, and the other, because these same extremities are the organs of touch.] In addition to the spinal accessory nerves, which may be now seen to arise from each side of the medulla spinalis in the upper half of the neck by twelve or fourteen small fila- ments, and to ascend behind the ligarnenta denticulata, the spinal cord gives origin to at least thirty pair. ORIGIN OF THE SPINAL NERVES. The spinal nerves are symmetrical ; there are thirty pair, (some anatomists enumerate thirty-one or thirty-two,) which are divided into eight cervical, twelve dorsal, five lumbar, and five sacral ; all these nerves arise and termi- nate nearly in a similar manner; each spinal nerve is at first composed of two roots, an anterior and posterior, each of which consists of several filaments, which arise from the anterior and posterior surface of the spinal cord on either side of the median fissures; these filaments unite into fasciculi ; those composing the posterior root are larger than those in the anterior, (excepting in the case of the first or sub-occipital, whose anterior is equal or even larger than the posterior ;) these two fasciculi or roots are separated from each other by the side of the spinal cord, and by the ligamentum dentatum ; they can converge and proceed obliquely outwards and downwards to the dura rnater, which they perforate distinctly by two small open- ings, which, however, are so close, as to appear but one ; each fasciculus receives a sheath from the dura mater, they then pass through the inter- vertebral foramen, and in this situation a small oval ganglion is formed upon the. posterior root of each, to the surface of this ganglion the anterior root is only connected ; immediately on the outer side of this ganglion the two roots unite and form a single cord ; this is the proper spinal nerve ; after a short course out- wards, this divides into two branches, a posterior and an DUBLIN DISSECTOR. 311 anterior ; the former is almost universally the smaller, ex- cept in the case of the second cervical, and is distributed to the muscles and integuments posterior to the vertebral column ; the anterior branches of the spinal nerves are much larger ; they enter into several plexuses, and supply the muscles anterior to the spinal column, as also the ex- tremities. The superior cervical nerves take nearly a transverse course from their origin to the inter- vertebral foramina ; the succeeding nerves are more oblique, and the lumbar and sacral take a longitudinal course, and form their ganglions and subsequent divisions within the spinal canal. All the spinal nerves are compound nerves, but their roots are simple, the anterior being motor, and the poste- rior sensitive. The course and distribution of the spinal nerves shall be examined individually afterwards, the student may next dissect the brain from below. DISSECTION OF THE BRAIN FROM BELOW. THE brain, medulla oblongata, and the upper part of the spinal cord should be carefully removed from the subject ; the brain, with the base uppermost, should then be placed in a shallow basin ; the cerebellum and medulla oblongata will now fall a little backwards, and all the parts of the base of the brain will be exposed. Raise the pia mater from the forepart and sides of the medulla oblongata ; the several eminences on this organ may be traced upwards to the cerebrum, or to the cerebellum : to follow these, the dissector should rather scrape the surrounding substance with the handle or with the back of the knife, then cut it with the edge. In the description of the brain already given, certain differences between the cineritious and the white substances have been stated ; it is necessary to recol- lect that the former is soft, vascular, and pulpy, and that the latter is fibrous ; it is an opinion entertained by many, particularly Gall and Spurzheim, that the grey is the origin or matrix of the white substance, or that the former is a secreting organ, and the latter consists of fine conducting vessels or filaments : the direction of the fibres in some situations is very distinct ; some pass from below upwards and outwards ; these are termed diverging fibres, others pass from the surface or circumference downwards and inwards, these are the converging or uniting fibres: first proceed to trace these two orders of fibres in the cerebellum. 312 DUBLIN DISSECTOR. STRUCTURE OF THE CEREBELLUM. TRACE the restiform body upwards into the cms cerebelli ; divide this substance vertically, and the former may be seen continued into the mass of grey substance in the crus known by the name of corpus dentatum, or the ganglion of the cerebellum ; from the inner edge of this a narrow white fasciculus may be traced inwards towards the medi- an line ; it there unites with a similar process from the op- posite side, and both divide into several fine bands, which diverge and form the vermiform process, (or the primary portion of the cerebellum ;) the peripheral extremities of these fibres are covered by cineritious substance, and pre- sent, when cut vertically, an arborescent appearance; the remainder, or the principal portion of the restiform body, passes upwards and outwards through the corpus dentatum, and then divides into several processes or stalks which di- verge through each hemisphere and sub-divide into finer branches, each of which is covered by the grey substance on the surface ; a vertical section of either hemisphere presents also that arborescent appearance known by the name of arbor vitse. The converging fibres of the cere- bellum are inferior and superior ; the latter are very deli- cate and rather indistinct in their course ; they consist of several fibres which issue from the vermiform process and unite in one broad lamina which is thin in the centre, (the valve of Vieussens,) and thick at each side (processus a cerebello ad testem ;) thus these superior converging fibres form the superior or lesser commissure of the cerebellum, they also connect the cerebellum to the quadrigeminal bodies. The inferior converging fibres are more distinct, they proceed from the cineritious substance in either hemisphere forwards and inwards, and form the principal portion of each crus cerebelli ; they then pass transverse- ly across the pons Varolii and unite with those from the opposite side ; thus the superficial lamina or the transverse fibres of the pons form the great or inferior commissure between the hemispheres of the cerebellum. STRUCTURE OF THE CEREBRUM. REMOVE the pia mater from the anterior pyramids of the medulla oblongata, and separate these from each other, the decussating fibres will be seen ; through these the py- ramid on one side may be said to arise from the spinal cord of the opposite side ; as the pyramids approach the pons they are somewhat contracted ; on entering this substance they separate into fasciculi, which intermix with cineri- tious substance ; they are considerably increased in size and DUBLIN DISSECTOR. 313 number in passing through the pons, and they then form the anterior and external two-thirds of the crura cerebri. The olivary body and a few fibres from the restiform ot each side also ascend through the pons behind the fasci- culi of the pyramids ; these also increase in size in passing through the pons, and then enter the crura cerebri, the posterior and internal part of which they form. Each crus cerebri contains a mass of cineritious substance of a pecu- liarly dark colour, in passing through which the white fibres appear increased in quantity. The posterior and internal fasciculi of each crus ascend and pass into those masses of grey substance called the optic thalami, and the corpora striata ; in passing through these their fibres are increased in number, and thence extend in a radiated man- ner into the posterior and superior convolutions of each hemisphere, where they are covered by a layer of grey substance. The anterior and external portion of each crus, which is in continuation with the corpus pyramidale, in like manner ascends and expands into fasciculi, which may be traced into the inferior, anterior, and external convolu- tions of each hemisphere. The uneven surface known by the name of convolutions appears to depend on the unequal length of these diverging fibres; if they were all of equal extent the surface of the cerebrum would be smooth, but as some fall short of others, and all are covered by the grey substance, an uneven or convoluted surface is the result. From this grey substance which covers the surface of each convolution, the converging or descending fibres are de- scribed as arising, and thence passing towards the mesial line to unite with those from the opposite side ; the corpus callosum and the anterior and posterior commissures are supposed to be thus formed ; in addition to these trans- verse processes there are several other parts which may serve as media of communication between different parts in each hemisphere of the brain, viz. the fornix, the tsenia semicircularis, the pineal gland, and its pedunculi, the in- fundibulum, the septum lucidum, &c. &c. VESSELS OF THE BRAIN. THE brain is supplied with blood by the two vertebral, and the two internal carotid arteries. The vertebral arteries are the first branches of the subclavian arteries, they as- cend through the series of foramina in the transverse pro- cesses of the cervical vertebrae, and passing through the foramen magnum into the cranium, they proceed obliquely forwards and inwards, and end in a common trunk called the basilar artery ; each vertebral first sends off two long and delicate branches, one on the anterior, the other on the 27 314 DUBLIN DISSECTOR. posterior surface of the spinal cord, these extend the whole length of this organ, supplying it with blood, and sending out small branches along the several spinal nerves. [Of these two arteries, the latter, the posterior vertebral, continue the whole length of the spinal cord parellel to each other, but the former, the anterior vertebral arteries, soon after their origin unite and form a single trunk, which descends along the anterior middle fissure of the cord.] Next to these branches each vertebral gives off the infe- rior artery of the cerebellum; this turns backwards be- tween the pneumogastric and spinal accessory nerves, and is distributed to the inferior surface of the cerebellum. The basilar artery ascends along the median groove in the pons, and at its superior edge divides into four branches, two for each side, viz. the superior cerebellar artery and the posterior cerebral ; these are distributed as their names imply : the posterior cerebral artery of each side is joined by the posterior branch of each internal carotid ; this communication completes the circle of Willis. Each in- ternal carotid artery winds obliquely forwards, upwards, and inwards, through the tortuous canal in the temporal bone, and through the cavernous sinus ; beneath the anterior cli- noid process it perforates the dura mater, and rises perpen- dicularly to the base of the brain between the second and third nerves, and then divides into three branches, the an- terior, middle, and posterior; before it thus divides it gives off, first, small branches to the cavernous sinus and to the dura mater, and next the ophthalmic artery which enters the orbit through the optic hole, and is distributed to the eye and its appendages. The anterior branch of the caro- tid is also named the anterior cerebral artery, or the artery of the corpus callosum : this passes for wards and inwards, and is joined to the corresponding artery of the opposite side by a short branch, (the anterior communicating ar- tery,) it then ascends and runs along the upper surface of the corpus callosum, distributing its branches to the in- ner surface of each hemisphere ; the middle branch [the middle cerebral artery] of the carotid is very large, it passes upwards and outwards deep in the fissure of Syl- vius, and is distributed to the anterior and middle lobes of the cerebrum ; the posterior branch of the carotid is named the posterior communicating artery ; it is small, passes backwards, and joins the posterior cerebral artery ; this forms the side of the circle of Willis. (See Anatomy of Vascular System.) The vessels of the brain are accompa- nied by numerous fine filaments of the sympathetic nerve, DUBLIN DISSECTOR. 315 these pass into its substance and supply its intimate struc- ture. The veins of the brain join the sinuses which have been already described ; the principal veins are on the superior surface of the brain, whereas the large arteries are below. The brain and its membranes exhibit many morbid ap- pearances. The dura-mater is sometimes found in a state of inflammation ; to an inexperienced eye this appearance is difficult of detection, as in this condition, very few vessels more appear carrying florid blood, than in the natural state; in injuries from external violence, where inflamma- tion follows, suppuration often occurs, and the pus is found sometimes on its external surface, between it and the bone, in other cases the matter is internal, and then the arach- noid coat, lining the dura mater, is found covered with pus. Scrofulous and fungoid or fibrous tumours growing from the dura mater, producing absorption of the bone, or pressure on the brain, are occasionally found : also a deposition of bony lamina? in some part of the dura mater, more parti- cularly in the falciform process or near the superior longi- tudinal sinus. The arachnoid membrane is sometimes inflamed. Arachnitis, when chronic, presents an opaque or in some in- stances a thickened state of the membrane, which gives it a tolerably firm consistence ; serous fluid, sometimes of a gelatinous nature, and creamy appearance, is found be- tween it and the pia mater; and although these appear- ances are said to depend on inflammation, still no vessels holding red blood are found ramifying on its surface, the redness which is sometimes present, being owing to the vessels of the pia mater appearing through it. Adhesions between the parietal and visceral lamina? of this membrane seldom occur, as in other serous cavities : in acute arach- nitis, pus, or sero-purulent fluid, or serum with lymphy flakes and of a sanguineous colour is often effused. Hydroceplialus is a disease of this membrane of frequent occurrence, it consists of an effusion of clear serous fluid, it may be acute or chronic, and the fluid, which may amount to a few ounces or to as many pounds, may be collected either within the ventricles, (hydrocephalus internus,) or it may be on the surface of the brain, (hydrocephalus exter- nus ;) in the latter the brain will be found compressed to- wards the base of the cranium, in the former, which is the more common form, the hemispheres will be found expand- ed; in both the cranium will be enlarged, and in young persons the sagittal and coronal sutures will be expanded, and the fluid, in passing from one lateral ventricle to the other, raises up the fornix, expands the foramen commune 316 DUBLIN DISSECTOR. anterius, and so passes into the third and thence into the fourth ventricle. In hydrocephalus, scrofulous disease is frequently to be found at the base of the brain, as also small tubercles on the pleura and peritonseum. We often find fluid also between the arachnoid coat and the pia ma- ter ; sometimes effused in small patches between these two membranes, and at others over a large extent ; when this anasarcous-like effusion takes place, the vessels of the pia mater are found more distended with blood than usual, and the arachnoid membrane is thick and opaque ; in most cases where this effusion takes place, water is also secreted in the lateral ventricles, and in the sheath of the vertebral canal. There is some difficulty experienced in distinguishing inflammation of the pia mater on account of the great num- ber of small vessels which naturally ramify on it ; how- ever, in the inflamed state they become much more numer- ous, and by their anastomoses, make a beautiful reticulated appearance, not however, causing such a general redness as may be observed in the inflammation of some other membranes ; and when the inflammation runs high, pus is formed, which is effused on the whole upper surface of the brain. A common morbid appearance found in the pia mater is the formation of small cysts, containing water, which are generally called hydatids ; these are found more usually on the choroid plexus, and in the velum interposi- tum. Inflammation of the substance of the brain is occasion- ally observed arising from external injury ; the redness, which is generally slight, is confined to one particular part; in this state, when cut into, the colour appears to arise from a great many small vessels which are filled with red blood ; the inflamed part is softer and more yielding than natural, giving rise to an appearance which has been lately described by French writers, and called "ramollis- sement ;" when the inflammation proceeds further, abscess- es holding pus are formed, which, if of a large size, break down the substance of the brain, and present a very jagged appearance on their internal surface. Apoplexy, or an ef- fusion of blood or serum either on the surface or in the substance of the brain, is also to be met with, and occa- sionally into some of the ventricles ; the blood found in those situations is almost always black and coagulated, the substance of the brain is torn ; when the person survives the attack, and recovers the energy of the organ, the blood becomes absorbed in part, a regular cyst or cell encloses the remainder, and in some cases no trace remains of the original disease, except some condensed or cicatrized ap- pearance. Deposition of caseous and even of earthy matter DUBLIN DISSECTOR. 317 in the arteries of the brain may also be looked for ; this appearance is by no means rare, particularly in old sub- jects ; arising from this state of the arteries, aneurisms of the internal carotids are described by some authors, but they are not of common cccurrence. CHAPTER III. DISSECTION OF THE NERVES. THE course and ultimate distribution of most of the nerves have been already mentioned in the description of the muscles and of the several regions of the body ; in the present chapter they shall be considered in a systematic manner, commencing with the cerebral nerves, the origins of which have been already described. SECTION I. DISSECTION OF THE CEREBRAL NERVE8. 1. OLFACTORY nerves; from the bulb, which each of these nerves forms at the side of the crista galli, several branches descend into the nose, through the foramina, in the cribriform plate; they may be divided into the inter- nal, middle, and external. The internal branches, about ten in number, descend in grooves along the septum, subdivide into many filaments which form a plexus with each other in the mucous membrane ; some of these can be traced nearly to the floor of the nose. The middle branches are distributed to the mucous membrane lining the roof of each nostril. The 'external branches descend along the grooves on the turbinated bones, dividing and communicating fre- quently with each other, so as to form numerous plexuses, which are lost in the pituitary membrane. All the branch- es of the olfactory nerves are very soft in the cranium, but in passing through the ethmoid bone they each receive a sheath from the dura mater, which is ultimately lost in the external layer of the mucous membrane. (See the Ana- tomy of the Nose.) 27* 318 DUBLIN DISSECTOR. II. OPTIC NERVES ; each optic nerve on passing through the optic foramen, becomes surrounded by a strong sheath, derived from the dura mater ; the four rectt muscles next surround it, from the fleshy portions of which it is separa- ted by a considerable quantity of soft fat, in which several nerves and vessels are lodged ; from the optic foramen this nerve proceeds forwards and a little inwards, so as to be slightly curved, the convexity outwards ; at the back part of the eye it is very much constricted ; it then pierces the sclerotic and choroid membranes and terminates in the retina. (See Anatomy of the Eye.) The ophthalmic ar- tery accompanies this nerve, in the optic foramen it lies beneath it, it afterwards twines around it to its internal side. [This artery gives off the central artery of the retina, which perfo- rates the sheath of the nerve, and gets into the substance of the nerve, with which it passes to the ball of the eye to be variously distributed.] In addition to the dura mater, this nerve possesses a very dense neurilema which sends in numerous processes to form small canals or tubes in which the nervous substance is contained, so that this nerve is not composed like other nerves, of several filaments placed parallel to each other ; if the white substance be removed by maceration in an alkali, its cellular structure will become obvious. At the side of the body of the sphenoid bone, the follow- ing four nerves of the orbit lie according to their numeri- cal order, viz. most superiorly the third pair, then the fourth, next the ophthalmic branch of the fifth pair, and most inferiorly the sixth or abducens nerve ; they are here closely united to each other, forming what may be termed the orbital plexus, until they arrive at the anterior clinoid process, where they separate, and as they are entering the foramen lacerum orbitale they lie thus ; most superior is the fourth, then the frontal branch of the ophthalmic, next the superior division of the third, external to which, and near to the outer wall of the orbit, is the lachrymal nerve of the ophthalmic, after these the nasal nerve, below which is the inferior division of the third, and lastly, lying infe- rior to them all, holding the same relation to them as at the cavernous sinus, is the sixth nerve; to this last the ascend- ing branches of the superior cervical ganglion of the sym- pathetic nerve are intimately connected, and several fila- ments from these can be traced into the orbital plexus. To expose these four nerves the orbit should be opened, which is to be done by dividing the orbital plate of the os frontis by two cuts with the saw, these should unite in the optic foramen; the internal is to be carried forward to the DUBLIN DISSECTOR. 319 superciliary arch about half an inch external to the inter- nal angular process ; the external incision is to be carried deeply through the malar bone; a slight blow with the hammer will then throw fowards the roof of the orbit, and the bone will separate easily from the periosteum. III. The THIRD PAIR, or motores oculorum, in passing through the foramen lacerum orbitale, divide into two branches, a superior and inferior ; the superior, or the small- er, passes between the heads of the external rectus muscle and over the optic and nasal nerves, and divides into two branches, the smaller and shorter one of which supplies the superior rectus, the other the levator palpebrse muscle. The inferior or the larger branch passes below and to the outside of the optic nerve, and divides into three branches, an internal, middle, and external ; the internal is the lar- gest, it passes obliquely downwards, forwards, and in- wards, beneath the optic nerve, and getting to its internal side is distributed to the internal rectus, the middle to the inferior rectus ; and the external, which is the longest, pass- es downwards and forwards on the surface of the inferior rectus, between it and the globe of the eye, (it gives no fil- aments to this muscle,) and is lost in the inferior oblique muscle ; this last branch gives off from its root a small short filament to the ophthalmic ganglion. All the branches of the third pair are distributed to the ocular surfaces of the five muscles they supply. IV. The TROCHLEATOR, or fourth nerve, having entered the orbit by the foramen lacerum, ascends obliquely for- wards and inwards above the levator palpebrre and the superior rectus, and is distributed by four or five fine branches to the upper or orbital surface of the superior oblique muscle : as this delicate nerve is passing along the outer side of the cavernous sinus, it lies between the third pair and the ophthalmic branch of the fifth, below the for- mer and above the latter and the sixth; as it enters the orbit it mounts above the third and fifth, a fine filament usually connects it to the latter, it is then the highest nerve in the orbit, both it and the frontal being immediately be- neath the periosteum ; previous to entering the oblique muscle its size is somewhat increased. V. THE TRIGEMINI, or the fifth pair, having formed the semilunar or Casserian ganglion, divides into three, the ophthalmic, the superior and inferior maxillary nerves. The OPHTHALMIC NERVE passes along the outer side of the cavernous sinus below the third and fourth, and above the sixth ; in this situation it receives some filaments from the sympathetic nerve ; as it approaches the foramen lace- rum orbitale, it divides into three branches, the lachrymal, 320 DUBLIN DISSECTOR. frontal, and nasal, which are situated with respect to the other nerves as above described. The lachrymal nerve, the smallest and most external of the three, passes forwards and outwards to the lachrymal gland above the external rectus muscle, and beneath the perios- teum, but gives no branches to this muscle ; it is surround- ed by fat and accompanied by the lachrymal artery ; it sends off, in this course, two small branches, one through the spheno-maxillary fissure to communicate with the su- perior maxillary nerve, and the other through the malar bone, to communicate with the facial nerve ; near the gland the lachrymal nerve enlarges and sends four or five branches to its inferior surface, and it then terminates in several fine soft filaments on the conjunctiva, lining the superior palpebra and cellular membrane between the gland and malar bone. The frontal nerve enters the orbit, between the superior rectus and the periosteum, along with the fourth but infe- rior and external to it ; it passes forwards in a kind of groove on the upper surface of the levator palpebrse mus- cle ; and near the superciliary arch it divides into two branches, an internal and external ; the internal or supra- trochleator nerve, the smaller branch, runs forwards and in- wards above the trochlea of the superior oblique muscle, and is distributed to the corrugator supercilii, orbicularis palpebrarum,andoccipito-frontalis muscles, also to the in- teguments of the forehead and superior eyelid ; it commu- nicates with the infra-trochleator branch of the nasal nerve, and sends one or two small filaments into the frontal sinus. The external branch, or the supra-orbital or proper frontal nerve, appears as the continuation of the original trunk, both in size and in direction, it passes through the super- ciliary notch or foramen, ascends on the forehead divides into two branches which subdivide into numerous fila- ments, these chiefly ascend in the muscles and integuments of the scalp, many of them take a very long course, and communicate with the portio dura, with the occipital nerves, and with those from the opposite side. Neither the frontal nor lachrymal nerve gives any motor filaments to the mus- cles in the orbit. The nasal nerve separates from the frontal behind the or- bit, enters this cavity beneath that branch, and between the two heads of the external rectus, it then runs obliquely for- wards and inwards above the optic nerve and below the su- perior rectus muscle, and continues its course along the inner side of the orbit below the superior oblique muscle, and here divides into two branches, the external or the in- fra-trochleator nerve, and the internal or the nasal ; the DUBLIN DISSECTOR. 321 nasal nerve, previous to its entrance into the orbit, is joined by a filament from the sympathetic nerve ; on the outer side of the optic, and just as it enters this cavity, it gives off a delicate branch about an inch in length, which runs along the outer side of the optic nerve to the lenticular ganglion ; as the nasal nerve passes over the optic it gives off two ciliary nerves. The infra-trochleator nerve runs for- wards beneath the pulley of the oblique muscle, and di- vides into several filaments which communicate with the supra-trochleator nerve, arid are distributed to the lachry- mal passages, and to the integuments and muscles on the side and dorsum of the nose. The internal branch or the proper nasal passes through the anterior of the internal or- bital holes into the cranium, crosses the cribriform plate, and descends by the side of the crista galli into the nasal fossa3 where it divides into posterior and anterior filaments ; the former are distributed to the septum, the latter descend behind the nasal bones, and are lost in the integuments at the tip of the nose. The sixth pair of nerves should be next dissected, as it is distributed along with the preceding nerves in the orbit. SIXTH or ABDUCENS NERVE, after traversing the cavernous sinus (where it is joined by branches from the sympathetic nerve) on the outer side of the carotid artery, enters the orbit through the lower part of the foramen lacerum be- tween the origins of the external rectus, beneath the other orbital nerves and above the ophthalmic vein ; it then passes forwards and outwards, and is distributed to the ocular sur- face of the external rectus muscle. All the motor nerves in the orbit are distributed to the same surface of their re- spective muscles, except the fourth, which spreads its branches on the orbital surface of the superior oblique muscle. The student should next examine the lenticular or ophthal- mic ganglion ; this small body is situated near the back part of the orbit between the optic nerve and the external rec- tus muscle ; it is of a reddish colour and surrounded by soft fat ; its posterior superior angle receives the filament before mentioned from the nasal branch of the ophthalmic, and its posterior inferior angle receives the twig from the inferior oblique branch of the third pair ; these two nerves are described by some as forming this ganglion ; from the anterior angles of this ganglion two fasciculi of fine nerves proceed, termed the ciliary, the inferior fasciculus is larger than the superior. The ciliary nerves are about twenty in number, eight or ten in the inferior fasciculus, about six in the superior, and three or four internally, which arise from the nasal nerve ; the ciliary nerves twine along the surface 322 DUBLIN DISSECTOR. of the optic nerve, accompanied by the ciliary arteries, and pierce the back part of the sclerotic coat, they then be- come flat, and proceed forwards in parallel grooves on the inner surface of that membrane, with very little connexion to the choroid coat ; at the anterior part of the eye they meet the ciliary ligament, in this substance most of these nerves are lost, hence some consider this as a ganglion ; on each side, however, one or two branches may be traced through this into the iris, in which they divide into numer- ous filaments of extreme minuteness. The several nerves of the orbit have different offices to discharge ; no less than seven nerves are engaged in the op- tic apparatus, viz. the second, third, fourth, sixth, and por- tions of the fifth, seventh, and sympathetic ; the respective office of each of these is probably as follows : the second is a sentient nerve, the seat of vision ; the third, fourth, aud sixth supply the orbital muscles with their voluntary or motor power ; branches of the seventh also impart the same to the sphincter oculi or orbicularis palpebrarurn ; the ophthalmic portion of tne fifth endows with sensation all the parts within the orbit, also the interior of the eye, the surface of the globe, the palpebraB, the lachrymal ap- paratus, the integuments of the forehead, &c. &c. The filaments of the sympathetic nerve serve to connect more closely the component parts of the orbital plexus with each other, and with the system at large, they also probably serve some useful purpose in reference to the ophthalmic ganglion, to which they are connected through the nasal nerve, the sympathetic being directly connected to or en- gaged in most of the principal ganglions in the body. The lenticular or ophthalmic ganglion also is interesting as to its connexions, as it in this respect resembles the ganglions on the spinal nerves ; thus, it has two roots, the third pair supplies the motor, while the nasal filament of the fifth which also carries the sympathetic connexion, imparts the sensitive quality ; the distribution also of the branches of this ganglion is in accordance with its component elements, inasmuch as they are distributed to one of the most deli- cately sensible, and one of the most active structures in the whole range of the animal economy, namely the iris, the muscular nature of which too may be inferred from the very circumstance of this peculiar nervous supply. The student should next proceed to examine the superior and inferior maxillary nerves, the remaining divisions of the fifth pair. Remove the outer wall of the orbit with the saw or hammer, make a vertical section of the nose and face, and separate the globe of the eye and its muscles DUBLIN DISSECTOR. 323 from their attachments ; below the cavity of the orbit the superior maxillary nerve may be seen. The SUPERIOR MAXILLARY NERVE passes from the middle of the Casserian ganglion forwards through the foramen rotundum into the pterygo-maxillary fossa ; it here sends off several branches, and then passing through the spheno- maxillary fissure it continues its course forwards along the infra-orbital canal to the cheek, where it terminates in the infra-orbital nerves ; in the pterygo-maxillary fossa it first sends down two small branches along the back part of the superior maxillary bone; these, after a short course, unite in a small triangular reddish substance called the splieno- palatine ganglion, or the ganglion of Meckel ; this ganglion is imbedded in fat, surrounded by the branches of the internal maxillary artery, and is situated on the external side of the nasal plate of the palate bone, which separates it from the cavity of the nose, behind the tuberosity of the superior maxillary bone, and in front of the pterygoid processes. Three sets of branches proceed from this ganglion, an infe- rior, internal, and posterior. First the inferior or the palatine nerves descend in the bony canal of that name, send some small twigs through this canal to the spongy bones, and near the palate separate into three filaments, an anterior, middle, and posterior ; the anterior passes forwards in a groove within the alveoli and above the mucous membrane, supplying the latter and sending small branches into the bone to the teeth : the middle and posterior filaments of the palatine nerve are distributed to the amygdalae, the soft palate, and the uvula. The internal branch, or the spheno- palatine nerve is very short, passes through the spheno- palatine hole into the upper and back part of the nose, and divides into five or six branches; the most of these pass im- mediately into the mucous membrane, covering the supe- rior and middle spongy bones, one branch called the naso- palatine nerve, or nerve of Cotunnius, passes beneath the sphe- rioidal sinus, and descends obliquely forwards along the septum nasi as far as the foramen incisivum, where it com- municates with the anterior palatine branches, and where some anatomists describe a small ganglion (naso-palatine) to exist ; this, however, in the human subject, can seldom be distinguished from the surrounding fat and vessels. The third or the posterior branch of MeckeFs ganglion is the Vidian nerve ; this passes backwards through the Vi- dian canal above the internal pterygoid plate, and sends some small filaments into the sphenoidal sinus ; it then perforates the cartilaginous substance that closes the fora- men lacerum anterius, enters the cranium, and divides into two branches, an inferior and superior ; the inferior or ca- 324 DUBLIN DISSECTOR. rotid branch enters the cavernous sinus, and joins the plexus formed in this sinus around the artery by the as- cending branches of the superior cervical ganglion of the sympathetic; the superior branch runs backwards and out- wards beneath the dura mater and Casserian ganglion in a groove on the petrous bone, enters the hiatus Fallopii in this bone, and becomes attached to the portio dura nerve, which it accompanies as far as the back part of the tym- panum ; the Vidian nerve then leaves the portio dura, re- ceives the name of corda tympani, and enters the typanum a little below the pyramid ; it now proceeds forwards be- tween the long leg of the incus and the handle of the mal- leus, to the latter it is firmly connected ; it then escapes by the hole in the glenoid fissure along with the tendon of the laxator tympani muscle ; it next runs downwards, inwards, and forwards, joins the gustatory nerve, and continues at- tached to it as far as the submaxillary gland ; it now leaves the gustatory nerve and unites with some filaments from it in the submaxillary ganglion, which is situated near the pos- terior edge of the submaxillary gland, and from which a number of filaments proceed ; these form a plexus which supplies this gland. As this Vidian or recurrent nerve takes this singularly intricate course, it goes under differ- ent denominations, and serves to maintain several interest- ing communications ; for example, it connects the cervical ganglions of the sympathetic nerve with the spheno-pala- tine, also the latter with the submaxiliary ganglion, it also joins the superior and inferior maxillary nerves to one an- other and both to the portio dura ; the nervous supply to the muscles of the palate also is thus connected to the por- tio dura, the great muscular nerve of the face, &c. The superior maxillary nerve immediately after, and sometimes previous to giving off the two descending branches which join the spheno-palatine ganglion, sends off the orbital branch, this ascends through the spheno-max- illary fissure and divides into two branches, the malar and temporal; the malar communicates with the lachrymal nerve, passes through a small canal in the malar bone, and is distributed to the integuments and muscles covering the malar bone ; the temporal branch also passes through the malar bone into the temporal fossa, pierces the temporal fascia, becomes cutaneous, and joining some branches of the facial nerve, it accompanies the temporal artery, and is lost in the integuments of the temple and head. The su- perior maxillary nerve next gives off the posterior dental nerves ; these are two or three branches which wind round the tu berosity of the maxillary bone, enter small foramina, which lead to the posterior alveoli in this bone, and supply DUBLIN DISSECTOR. 325 the molar teeth ; some branches also supply the gums and the buccinator muscle. As the infra-orbital nerve, which is the last branch of the superior maxillary, proceeds along the floor of the orbit, it sends off' some small filaments to the fat and muscles in this region, also the anterior-dental ; this descends along the fore part of the antrum, to the lining membrane of which it gives some fine filaments and is then lost in several branches which supply the canine and incisor teeth : the infra-orbital nerve then escapes through the foramen of the same name, beneath the orbi- cularis palpebrarum and levator labii superioris alseque nasi muscles ; it here divides into several branches which are distributed to the face, some of these ascend to the pal- pebrse, others pass outwards to the cheek, and the largest branches descend to the ala nasi and to the upper lip ; these different branches have frequent communications on the side of the face with the portio dura, on the nose with the nasal nerves, and on the buccinator muscle they form a plexus with each other and with the buccal and facial nerves. The INFEKIOR MAXILLARY NERVE ; this, which is the third and largest branch of the fifth pair, immediately passes from the ganglion through the foramen ovale into the zygo- matic fossa behind the external pterygoid muscle, where it divides into two large branches, a superior or external, and an inferior or internal. The inferior maxillary nerve con- sists of two portions, one is plexiforrn and sensitive, and proceeds from the Casserian ganglion, the other is conceal- ed by this, and consists of white parallel fibres which do not pass through the ganglion ; this is the motor portion of this nerve ; in the zygomatic fossa this small deep por- tion winds round the other, becomes anterior to it, and both unite inseparably ; the nerve then divides into two branches, superior and inferior. The superior or external retains the motor portion of the trunk, and immediately subdivides into four set of branches, viz. the deep temporal, massete- ric, buccal, and pterygoid ; the inferior or internal division of the nerve is the larger, and subdivides into the auricu- lar, inferior dental, and gustatory nerves, which are pro- bably all nerves of sensation. First, the deep temporal nerves are two in number, an anterior and posterior, they ascend between the temporal bone and muscle, and are lost in the latter ; some small branches escape through the temporal fascia and communicate with the cutaneous temporal nerves. Second, the Buccal nerve arises in general in com- mon with one of the last, it passes forwards and down- wards between the pterygoid muscles, to the external of which, and to the temporal, it sends some branches, it then 28 326 DUBLIN DISSECTOR. passes between the coronoid process and the buccinator mus- cle, and on the latter it divides into several long branches which form a plexus on this muscle with branches of the fa- cial and infra-orbital nerves. Third, the masseleric branch descends obliquely backwards and outwards through the sigmoid notch of the inferior maxilla, between the tempo- ral muscle and the neck of the lower jaw, close to the lat- ter, to which also it sends some filaments ; it is lost in the substance of the masseter muscle. Fourth, the pterygoid branches are two or three delicate branches, which descend to the pterygoid muscles. Thus the muscular portion of the trunk of the inferior maxillary nerve can be traced into those muscular branches, which supply the live great muscles of mastication on each side. The inferior division of this nerve divides into three branches, viz. the auricular, dental, and lingual or gusta- tory nerves ; first, the auricular or temporo-auricular branch ; this passes backwards and outwards behind the neck of the lower jaw, and before the meatus auditorius ; it here communicates with the facial nerve, and sends small fila- ments to the meatus and to the cartilages of the ear, also to the articulation of the lower jaw ; it then ascends through the parotid gland over the zygoma and divides into an an- terior and posterior branch which follow the divisions of the temporal artery, communicate with the facial nerve, and are lost in the integuments on the anterior and lateral parts of the head. Second, the inferior dental nerve sepa- rates from the gustatory, and is connected to it by a small twig, it then descends extern il to it, at first between the two pterygoid muscles, then between the lower jaw and the internal pterygoid ; it is here separated from the latter by the internal lateral ligament ; about the middle of the in- ternal surface of the ramus of the jaw it sends off a small filament, the mylo-Jnpid nej've, this descends obliquely for- wards, confined in a groove in the bone by an expansion from the internal lateral ligament ; near the chin it divides into small branches from the mylo-hyoid, genio-hyoid, and digastric muscles, the adjacent cellular tissue and lympha- tic glands. The dental nerve then enters the canal in the lower jaw, which extends from the dental foramen oblique- ly forwards beneath the teeth as far as the chin ; in this course, this nerve, which is .'tccompanied by the dental vessels, supplies each of the molar and canine teeth with soft delicate twigs, and at the mental foramen it divides into two branches, one continues its course within the bone beneath the incisor teeth, the other is the mental nerve; this escapes by the mental foramen, bends upwards, and divides in a radiated manner into several branches which DUBLIN DISSECTOR. 327 pass to the muscles, mucous membrane, and integuments of the lower lip, and communicate with the facial nerve. Third, the lingual or gustatory nerve is smaller than the dental, to which it is connected by a short branch which encloses a space through which the internal maxillary ar- tery passes; beyond this branch of communication, the corda tympani (which has been before traced from Meek- el's ganglion) joins the gustatory nerve at an acute angle ; the latter is increased in size at this spot ; the gustatory nerve is here situated between the external pterygoid and the muscles of the palate and pharynx ; it then descends obliquely forwards between the internal pterygoid and the ramusofthe lower jaw; it next turns forwards above the sub-maxillary gland and the mylo-hyoid muscle, and lies on the mylo-hyoidean attachment of the superior constric- tor of the pharynx, and on the mucous membrane of the mouth and the stylo-glossus muscle, and accompanies the Whartonian duct; it then ascends above the sublingual gland, and becomes attached to the lateral and anterior parts of the tongue. In this arched course the gustatory nerve gives off, first, one or two small filaments to the in- ternal pterygoid muscle ; second, several to the tonsils, to the muscles of the palate, to the upper part of the pha- rynx, and to the mucous membrane of the gums; third, the corda tympani, and some accompanying filaments to form a plexus which supplies the sub-maxillary gland; fourth, a few branches which descend along the hyo-glos- sus muscle to communicate with the ninth or the lingual nerve ; fifth, a fasciculus of nerves to the sublingual gland, and to the surrounding mucous membrane ; lastly, at the tongue, it divides into several branches, some pass deep into the tissue of this organ, others long, fine and soft, rise towards its surface, and are lost in the mucous membrane and in the small conical papillae near its tip. The SIXTH PAIR of nerves have been described at page 321. VII. FACIAL NERVE or PORTIO DURA of the seventh pair; as this nerve is passing along the aqueduct of Fallopius in the temporal bone it receives superiorly the Vidian nerve; at the back part of the tympanum it sends off that nerve again, which then receives the name of corda tympani, here it also sends off small twigs to the tensor tympani and stapedius muscles ; as it escapes by the stylo-mastoid fora- men it gives off three branches, the posterior auricular, stylo-hyoid, and sub-mastoid ; the first, or the posterior auri- lar, bends upwards and backwards behind the cartilage of the ear, to which it sends several long branches, others also pass backwards to the integuments covering the mastoid 328 DUBLIN DISSECTOR. process and occipital bone ; the second, or the stylo-Jiyoid nerve is distributed to the digastric and styloid muscles, and anastomoses with the sympathetic and glosso-pharyn- geal nerves ; the third, or the sub-mastoid branch perforates the posterior belly of the digastric, supplies it with several filaments, and then communicates with the glosso-pharyn- geal nerve around the jugular vein close to the base of the cranium; other filaments descend and join the laryngcal branches of the pneumo-gastric nerve. The facial nerve then turns forwards across the external carotid artery and through the parotid gland ; in this substance it divides into two large branches, the superior or larger is called tempo- ro-facial ; the inferior, which is smaller, the cervico-fu- cial; these two branches take different directions, but are still connected together by cross branches which interlace with each other in a plexiform manner ; this plexus is named parotidean plexus, or pes anserinus. The temporo-fa- cial nerve ascends obliquely forwards across the neck of the lower jaw ; it first communicates with the auricular branch of the inferior maxillary nerve, and then divides into three fasciculi, the temporal, malar, and buccal ; these nerves take that course which their name implies ; they are all re- markable for the plexiform arrangement of their branches, and for their frequent communications with each other, and with the three divisions of the fifth pair, which are distributed to the face. The cermco-facial nerve descends obliquely forwards through the parotid gland towards the angle of the jaw, where it is only covered by the skin and platysma ; this nerve also divides into many branches, which may be arranged in three fasciculi, the maxillary, the sub-maxillary, and the cervical ; the first, or the maxillary, cross the ramus of the jaw and the masseter muscle, and communicate in the muscles of the lower lip with the men- tal nerve, and with the superior division of the seventh ; the second, or sub-maxillary, course along the base of the jaw, sending filaments to the integuments and superficial muscles, these also communicate at the chin with the men- tal nerve ; the third, or cervical branches, are very long and numerous ; they are distributed to the platysma and to the superficial muscles of the neck, and communicate with several filaments of the cervical plexus. The portio dura nerve has been ingeniously but erroneously supposed by Mr. Bell to be the nerve that excites the muscles of the face in particular conditions of respiration and in the ex- pression of passion, &c., hence he has named it the respi- ratory nerve of the face ; others more correctly consider the portio dura as the exclusive motor nerve of all the su- perficial muscles of the face. DUBLIN DISSECTOR. 329 VIL The AUDITORY NERVE or PORTIO MOLLIS of the seventh pair ; this simple nerve separates from the portio dura at the bottom of the meatus auditorius internus, and then di- vides into two branches, an anterior and posterior ; the an- terior passes forwards to the cochlea, penetrates through many small openings, and is distributed to the membrane covering its spiral lamina, and to that lining the canal on its axis: the posterior branch passes outwards, forms a grey swelling, from which proceed several filaments to supply the membrane lining the vestibule and semi-circu- lar canals. (See Anatomy of the Ear.) VIII. GLOSSO-PHARYNGEAL NERVE, the iirst and highest branch of the eighth pair ; this small and most probably a compound nerve, passes though the foramen lacerum pos- terius by a distinct canal, it then passes downwards and forwards anterior and internal to the jugular vein and in- ternal carotid artery, and behind the stylo-pharyngeus mus- cle ; it then winds round this muscle to its forepart, and descends obliquely inwards between it and the stylo-glos- sus to the posterior and lateral parts of the tongue ; in this course this nerve forms an arch nearly parallel to that which the gustatory and lingual nerves describe ; the glos- so-pharyngeal is smaller than either of these nerves ; it is situated between them, but deeper than either; and has very little if any, communication with them. As this nerve leaves the cranium it sends one or two small twigs into the temporal bone, these communicate with the caro- tid plexus in the cavernous sinus ; it is next attached to the facial, pneumo-gastric and sympathetic nerves by small filaments, which arc connected together by loose red- dish cellular membrane, and entangled with several small vessels. This nerve next gives off some branches to the pharyngeal plexus, some of these descend along the neck, and unite with the sympathetic and cardiac nerves, others ascend to the amygdala, and assist in forming the tonsillitic plexus ; as it approaches the pharynx, this nerve gives several branches to the stylo-pharyngeus and hyo-glossus muscles, also the superior and middle constrictors of the pharynx ; several filaments pass between these to the muco- us membrane of the pharynx and fauces, also to the folds or arches of the palate,, and to the epiglottis; the remain- ing branches of the glosso-p'haryngeal nerve are distributed to the muscular substance, large papillae, and mucous membrane at the root of the tongue ; the lingual branches are considered sentient, the muscular or pharyngeal both sentient and motor. PNEUMO-GASTRIC NERVE, or nervus vagus; this large com- pound nerve passes through the foramen lacerum in a 330 DUBLIN DISSECTOR. fibrous canal in common with the spinal accessory, but distinct from the last described nerve, and anterior to the jugular vein ; it then communicates with the spinal acces- sory, glosso-pharyngeal, lingual, facial, sympathetic and first and second cervical nerves ; to all these it is closely connected, and the nerve here has the compact appearance, and sometimes the greyish tint of a ganglion ; at first it is placed anterior to the vein and to the lingual nerve ; it soon, however, passes behind both and opposite the atlas, the vein separates it from the glosso-pharyngeal nerve which lies anterior to that vessel ; the vagus then descends along the forepart of the neck enclosed in the sheath of the ca- rotid artery and jugular vein : in this sheath it is placed be- tween these vessels, rather behind and more closely con- nected to the vein ; on the right side this nerve enters the thorax between the subclavian vein and artery, crossing the latter at right angles ; on the left side it is also anterior but nearly parallel to the subclavian artery, a little below which it crosses obliquely the back part of the arch of the aorta ; in the thorax these nerves descend at first obliquely backwards behind the roots of the lungs, and enter the pos- terior mediastinum, they then descend along the oesophagus through the diaphragm, and end on the stomach. The branches of each may be divided into cervical, thoracic, and abdominal ; the cervical branches are, the pharyngeal, superior laryngeal, cardiac and recurrent or inferior laryn- geal. First, the pharyngeal nerve arises from the vagus near the base of the cranium, and soon receives a twig from the spinal accessory ; it descends obliquely inwards behind the carotid artery to the side of the pharynx, divides into se- veral branches, which communicate with those from the glosso-pharyngeal, superior laryngeal, and sympathetic ; all these branches form the pharyngeal plexus ; this plexus extends along the side of the middle and upper constric- tors, and sends numerous filaments to each of these mus- cles, and to the mucous membrane of the pharynx and fauces. Second, the superior laryngeal nerve arises a little below the last ; it runs in an arched manner downwards and forwards behind the internal carotid artery, and below the superior cervical ganglion, with which it communicates, as also with the lingual nerve; it sends several filaments to the pharyngeal plexus, and then divides into two branch- es, external and internal ; the external is distributed to the sterno and hyo-thyroid, and to the other superficial mus- cles, also to "the thyroid body and to the cartilages of the larynx ; the internal perforates the thy reo-hyoid membrane and divides into numerous branches, many of these go to the anterior surface of the epiglottis, to the glands and mu- DUBLIN DISSECTOR. 331 cous membrane connected with it, also to the arytenoid glands and muscles ; one long filament descends obliquely forwards along the side of the larynx, beneath the thyroid cartilage, and supplies the crico-thyroid muscle. As the vagus descends it gives off tine filaments to the carotid ar- tery, some of which unite with the sympathetic and with the cervical nerves ; a little above the arteria innorninata the right vagus gives off, third, cardiac branches, these, two or three in number, join the cardiac nerves from the sym- pathetic ; the nerve of the left side does not send off so many or such large branches as that on the right side ; on the left side they accompany the carotid artery to the arch of the aorta, expand over it, and join the cardiac plexus. Fourth, the inferior laryngeal nerve, or recurrent ; that on the right side curves round the subclavian artery, ascends ob- liquely inwards behind the carotid and inferior thyroid ar- tery, along the side of the trachea to the larynx ; at its origin it gives off some cardiac filaments, afterwards some branches to the forepart of the trachea and the thyroid gland ; it then supplies the lower part of the pharynx, and ends in the posterior and lateral crico-arytenoid and in the thyreo-arytenoid muscles, also in the mucous membrane of the larynx on which it communicates with the superior laryngeal nerve. The recurrent nerve on the left side is much longer, it curves round the arch of the aorta behind the ligamentous remains of the ductus arteriosus ; it gives off several cardiac and pulmonary branches, and then ascends along the oesophagus and terminates in a similar manner to that on the right side. The pneumo-gastric nerves in their course through the thorax, pass behind the roots of the lungs, close to the bronchi, where they present an open plexiform appearance, and send off the pulmonary and O3sophageal nerves. The pulmonary branches arise from each vagus a little above the root of each lung ; a few of these branches pass to the forepart of the bronchial tubes, and form there a small plexus termed the anterior pulmonary plexus; this plexus communicates with the phrenic nerve, and sends its fine filaments along the pulmonary vessels to the lungs and pericardium ; the greater number of these pulmonic branches pass behind the bronchial tubes to the posterior pulmonic plexus ; near the root of the lung each vagus increases in size, its fibres divide, sub-divide, and re- unite in an areolar or plexiform manner, forming the poste- rior pulmonic plexus; this plexus is very large, lymphatic ganglia and vessels are entangled in it, and several branch- es from the sympathetic join it; its numerous filaments ac- company the bronchial tubes closely through the substance of the lungs. Below the root of each lung the fibres of 332 DUBLIN DISSECTOR. each vagus again approximate, and these nerves now be- come attached to the oesophagus, along which they descend to the stomach, the left on its anterior, the right (which en- tered the chest on a plane anterior to the left) on its poste- rior surface ; they frequently communicate with each other so as to encircle the oesophagus with a sort of plexus, which is named the cesophageal plexus, or plexus gula. On the stomach the right vagus, which is the largest, passes be- hind the cardiac orifice, to which it sends several small branches which unite with some from the left or anterior nerve; these form the cardiac plexus which encircles this part of the stomach; it then sends many long filaments to the muscular and mucous coats of the stomach, these com- municate with the solar plexus, also with the splenic, hepa- tic and renal. The left or anterior vagus spreads its branches along the anterior surface of the stomach and the lesser curvature ; several of these pass along the lesser omentum to the liver. The NERVUS ACCESSORIUS, or the third branch of the eighth pair; this nerve, in passing through the foramen la- cerum, is closely connected to the vagus ; below the base of the cranium it communicates with the eighth, ninth, and sympathetic nerves, passes behind the internal jugular vein, perforates the upper third of the sterno-rnastoid mus- cle, to which it sends some filaments, it then communicates freely with the cervical plexus, is increased in size, and supplies the trapezius, &c. This is supposed to be a com- pound nerve. IX. The LINGUAL NERVE, or the ninth, is a simple nerve, on escaping from the condyloid foramen it communicates with the eighth, the sympathetic, and the nervous arch or loop of the atlas ; it is at first posterior to the vessels and nerves in this situation, it then descends along their outer side, soon turns forwards, and becomes superficial to them ; it then takes the arched course of the digastric muscle across the neck, parallel but superficial to the lingual ar- tery, and arriving at the side of the base of the tongue above the os hyoides, it passes above the mylo-hyoid mus- cle and lies on the middle constrictor and on the hyo-glos- sns, at the anterior edge of which it divides into several filaments; some of these plunge : into the lingualis and genio-glossus muscles, others continue on to the point of the tongue, communicating with each other and supplying the muscular substance of this organ. As the lingual nerve is bending across the neck bdow the digastric tendon, it sends off a considerable branch, thn descendens colli, or noni; this nerve frequently receives a filament from the pneumo- gastric ; it descends along the forepart of the sheath of the DUBLIN DISSECTOR 333 carotid artery ; about the middle of the neck it is joined by the internal descending branches of the cervical plexus, with which it forms a small triangular plexus, the branches of which pass to the omo and sterno-hyoid and thyroid muscles; on the latter some filaments descend into the chest. Near the os hyoides the lingual nerve sends some filaments to the constrictors of the pharynx and to the stylo-pharyngeus, also one to the thyreo-hyoid muscle; on the surface of the hyo-glossus it gives off several branches to the surrounding muscles, some also to communicate with the gustatory branch of the fifth pair ; the lingual nerve then terminates chiefly in the genio-hyo-glossus muscle, and in the general muscular structure of the tongue, which organ it supplies with motor power. SECTION II. DISSECTION OF THE SPINAL NERVES. THERE are eight CERVICAL NERVES, the first passes out above the atlas, and is named the sub-occipital, the eighth passes out above the first dorsal vertebra. All these nerves immediately outside the inter-vertebral foramina, divide in- to a posterior and an anterior branch ; the posterior of each is smaller than the anterior, with the exception of the se- cond cervical nerve, whose posterior branch is very con- siderable, as it not only supplies the adjacent muscles, but also accompanies the occipital artery and its ramifications in the scalp ; the posterior branches of the other cervical nerves are small, they all communicate with each other, and are distributed to the integuments and muscles on the back part of the neck. The anterior branch of the first, or the sub-occipital passes forwards above the transverse pro- cess of the atlas, and supplies the adjoining small recti mus- cles, then descends before the atlas, and unites with the anterior division of the second cervical, so as to encircle the transverse process of that bone with a nervous loop ; in this course the sub-occipital is united by branches to the eighth and ninth, and to the superior ganglion of the sym- pathetic nerve ; with the latter nerve the anterior branches of all the spinal nerves regularly communicate. The an- terior branch of the second having received that from the first, descends and joins the anterior division of the third, this in like manner is connected to the fourth ; these anas- 334 DUBLIN DISSECTOR. tomoses between the anterior branches of the four superioi cervical nerves constitute the cervical plexus; the anterio; branches of the four inferior cervical are much larger thai those of the superior; they are united in like manner t each other, and to the anterior branch of the first dorsal and constitute the brachial plexus ; these two plexuses an< their branches the student may next dissect. The CERVICAL PLEXUS is formed by the anterior branche of the four superior cervical nerves, which join each othe in arches, from the convexities of which, branches aris< that again join in a similar manner; a quantity of cellula membrane is entangled in the areola? between these; thi: plexus is situated on the side of the neck, on a level wit! the second, third, and fourth vertebrae, between the sterno mastoid and trapezius muscles; it sends off severa branches which may be classed into ascending and de scending ; the former consist of superficial and deep, th< latter of internal and external ; the ascending superficia branches are two or three in number, they ascend obli quely forwards over the sterno-mastoid muscle, supply th platysma arid integuments over the parotid gland, also or the ear and on the side and back part of the head, ant communicate freely with the portio dura of the seventl pair of nerves ; one of these is much larger than the others is named superficialis or ascendens colli, it may be tracet chiefly from the third cervical, and is lost near the ear anc in the parotid gland ; this nerve accompanies the external jugular vein. The deep ascending branches of the plexuj are small nerves which supply the sterno-mastoid, digas trie, spleriius and adjacent muscles, and communicate witt the neighbouring nerves. The descending branches arc internal and external, the internal are two, a superficial and a deep ; the superficial internal descending brand: joins Ihe descendens noni, and assists it in supplying the superficial muscles on the forepart of the neck. The deep internal descending branch is the phrenic nerve: this arise* from the lower part of the plexus, chiefly from the fourth cervical, it has also in general a filament or two from the brachial plexus, [and a root from the third cervical nerve ;] the phrenic nerve, or, as it is also named, the internal res- piratory nerve descends obliquely inwards, on the anterior scalenus muscle. [At the junction of its roots from the third and fourth cervical nerves, it is at the outer edge of the scalenus muscle which it crosses obliquely, B.J as to enler the thorax at the inner edge of the muscle.] At the lower part of the neck it communicates with the lower cervical ganglion, and often with the vagus or its recurrent, it then enters the thorax between the subclavian DUBLIN DISSECTOR. 335 vein and artery, and descends to the diaphragm on the side of the pericardium between it and the pleura; the right phrenic is nearly perpendicular, the left takes an oblique course round the apex of the heart, it is therefore longer and lies more posterior than the right. On the diaphragm these nerves divide into several branches, some of which ramify on the superior surface of that muscle, others on its inferior accompanying the phrenic vessels. These branches on the right side send some filaments to the infe- rior vena cava and to the liver, and unite with the nerves of this organ and with those of the stomach ; on the left side the phrenic nerve sends some filaments to the esopha- gus and stomach, these communicate with the vagus and solar plexus. The external descending branches of the cervical plexus are numerous, some are superficial, others deep, the superficial descend to the clavicle and acromion process, supply the superficial muscles in their course, and terminate in the pectoral and deltoid muscles and in the integuments ; the deep branches descend behind the clav- icle, supply the deep muscles on the side of the neck and those connected to the scapula ; one of these branches is remarkable for its length, it is of the same size as the phrenic, and is named the external respiratory nerve of the trunk ; this nerve proceeds from the back part of the plexus, chiefly from the fourth cervical, it has also fila- ments connecting it to the third and second, and to the phrenic, it descends behind the scaleni muscles and be- neath the trapezius and levator anguli scapula?, and is al- most exclusively distributed to the serratus magnus muscle. The BRACHIAL [or AXILLARY] PLEXUS isformed by the junc- tion of the anterior branches of the fifth, sixth, seventh, and eighth cervical, and of the first dorsal ; this plexus is broad and flat, the nerves forming it are very large, particularly the inferior ; it is situated at the inferior and lateral part of the neck, between the scaleni muscles and above the subclavian artery, it then descends obliquely outwards be- neath the clavicle and subclavian muscle and over the first rib, into the axilla, where it rests on the serratus magnus behind the axillary artery and vein. The fifth and sixth cervical unite first, the seventh cervical runs alone for some distance, the eighth cervical and first dorsal unite imme- diately, so that, at first, this plexus consists of three roots, these "however soon unite; in the axilla they again sepa- rate and interlace [so as to surround the axillary artery like a braid,] and finally subdivide into the following branches, the thoracic, supra and sub-scapular, the inter- nal and external cutaneous, the median, ulnar, musculo- epiral and circumflex. 336 DUBLIN DISSECTOR. 1st. The thoracic branches arise principally from the up- per part of the plexus, they are four o.r live in number, and divide into anterior and posterior ; the former descend be- hind the clavicle in front of the axillary artery, subdivide into branches which accompany the thoracic arteries, sup- ply the pectoral muscles, and communicate with cutaneous branches from the intercostal nerves ; the posterior thoracic nerves descend behind the vessels to the serratus magnus, posterior scalenus and rhomboid muscles. 2nd. The supra-scapular nerve arises from the upper divi- sion of the plexus, descends obliquely backwards, parallel to the omo-hyoid muscle, to the superior costa of the scapu- la, and passes beneath the posterior ligament which con- verts the notch in this part of the bone into a foramen ; it then gives off a considerable branch to the supra-spinatus muscle, and proceeds beneath the acromion process and behind the neck of the scapula to the infra-spinous fossa, where it is distributed to the infra-spinatus and teres minor muscles. 3rd. The sub-scapular nerves are three or four in number, they arise from different parts, but chiefly from the upper division of the plexus, they descend behind the vessels, and ramify in the sub-scapular, latissimus dorsi, and teres major muscles. 4th. Internal cutaneous nerve is a long but delicate nerve, it arises out of the lower division of the plexus, descends nearly perpendicularly along the inner side of the arm, at first covered by the brachial aponeurosis, near the elbow it becomes cutaneous, and runs parallel to the basilic vein, and divides into two branches, an external and internal ; the external passes along the border of the biceps over the bend of the elbow to the fore arm, where it divides into several filaments, some of which descend in the integu- ments as low as the wrist, and communicate with the other cutaneous nerves ; this branch generally crosses the me- dian basilic vein, in some it lies superficial to it, in others behind it ; the internal branch descends towards the inter- nal condyle, and divides into several filaments, some of which descend along the inner, and others along the pos- terior part of the fore arm, they all terminate in the integ- uments. 5th. External cutaneous nerve, or musculo-culaneous or per- forans Casserii, is larger than the last, and arises from the upper division of the plexus, it descends obliquely out- wards, through the fibres of the coraco-brachialis, and be- tween the brachialis anticus and the biceps, it then de- scends along the outer border of the latter to the bend of the elbow, pierces the aponeurosis, becomes cutaneous, and DUBLIN DISSECTOR. 337 descends along the radial side of the fore arm to the wrist ; in the arm this nerve gives muscular branches to the cora- co-brachialis, biceps, and brachialis anticus, in the latter muscle it frequently communicates with the median nerve. At the elbow this nerve is situated between the biceps and supinator longus, and behind the cephalic vein, along the fore arm it accompanies this vein, and is often superficial to it ; near the wrist this nerve divides into an anterior and posterior branch, the former passes to the ball of the thumb and palm of the hand, the latter to its dorsum. 6th. Median or brachial nerve is the largest branch of the plexus, it generally arises by two roots, a small external one, which is in common with the external cutaneous from the upper part of the plexus, and a large internal one from the lower division of the plexus; the brachial artery in general separates these two roots, which soon unite into one thick cord. [I have seen one specimen, in which the first root above described, came off as usual, but the second came off by two fasciculi, which soon united to form a single trunk, after which the two roots extended down the arm about three inches, and then united over the brachial artery, so as to form the median nerve.] It descends obliquely outwards along the inner edge of the biceps, as far as the bend of the elbow, and in this part of its course it is covered only by the skin and fascia, si- tuated rather to the outer side of the artery above, crossing over it about the middle of the arm, and to its ulnar side below; at the b&nd of the elbow it passes deep between the supinator longus and pronator teres, and on the bra- chialis anticus perforates the pronator, and then descends along the middle of the fore arm, between the superficial and deep flexors, passes beneath the annular ligament of the carpus, where its size is increased, and terminates in the palm of the hand by dividing into five branches. In the arm the median nerve gives but few branches, these are small and unimportant ; in the fore arm it sends seve- ral considerable branches to the superficial and deep pro- nators and flexors, but not to the supinators, a little below the elbow it also gives off the anterior inter-osseal nerve, this accompanies the artery of the same name, along the anterior surface of the inter-osseous membrane, and supplies the deep flexors ; at the pronator quadratus it divides into two branches, one to supply that muscle, the other traverses the inter-osseous space, and is lost on the dorsum of the carpus and metacarpus : a little above the wrist, the me- dian nerve gives off a superficial branch, which passes over the annular ligament, and is lost in the integuments. In the palm of the hand, the median nerve divides into five 29 338 DUBLIN DISSECTOR. digital branches, the two first pass one along either side of the thumb, the third goes to the radial side of the index fin- ger, the fourth supplies the opposed sides of the index and middle finger, and the fifth, which is joined by a small branch from the ulnar nerve, supplies the opposed sides of the middle and ring fingers; these digital branches in the palm of the hand are superficial to the tendons, and form an arch nearly parallel to that formed by the ulnar artery, the branches of the latter and digital nerves then run to- gether to the extremity of each finger ; in this course they supply the lumbricales, the integuments of the hand and fingers, and near the last phalanx of each ; the nerves, en- large, become red and soft,, and divide into numerous fine branches, which are lost in the papilla? of the cutis. 7th. Ulnar nerve arises from the lower part of the plexus, descends obliquely backwards along the triceps, and be- hind the elbow joint, through the groove between the in- ner condyle and the olecranon process ; it then passes for- wards, and descends along the ulnar side of the fore arm to the carpus, and passing over the annular ligament close to the pisiform bone, ends in the palm of the hand, in two branches, a superficial and a deep. In the arm this nerve is superficial, and gives off a few branches to the triceps and to the skin ; in the fore arm it lies on the flexor pro- fundus, and between the flexor sublimis and ulnaris ; to these muscles, particularly the latter, it sends several fila- ments ; a little above the wrist it gives off the dorsalis car- pi ulnaris, a large branch which winds round the ulna to the back of the hand, and divides into several long branches which are lost in the integuments of that region and of the three inner fingers, and anastomose with the radial branch of the musculo-spiral nerve. Of the termi- nating branches of the ulnar nerve, the superficial is the larger, it divides into three branches, which supply the muscles and both sides of the little finger, also the ulnar side of the ring finger ; the deep palmar branch passes beneath the flexor tendons, runs across the metacarpus, and assists in forming a deep palmar arch, the branches of which are lost in the interossei muscles. 8th. Musculo-spiral nerve, is a very large nerve, it pro- ceeds from the middle and lower divisions of the plexus, descends obliquely backwards and outwards between the three portions of the triceps, round the humerus to its ex- ternal side, it then turns obliquely forwards and downwards towards the elbow, between the supinator longus and the brachialis anticus, and there divides into two branches, an an- terior or radial branch, and a posterior or interosseal branch. In its course down the arm this nerve sends several branch- DUBLIN DISSECTOR. 339 es to the triceps, a little above the outer condyle it gives off a large cutaneous branch [ramus superficialis dorsalis] which branch descends along the radial side of the fore arm to the thumb : at the bend of the elbow this nerve sends several branches to the long and short supinators, also to the extensors of the carpus ; on the surface of the supinator brevis it expands and divides into its terminating branches ; the anterior or the radial nerve [or ramus super- ficialis anterior] descends along the inner side of the supi- nator longus, which it supplies, and external to the radial artery; about the middle of the fore arm or a little lower, this nerve passes behind the tendon of the supinator longus, and becoming cutaneous descends behind the radius to the back of the hand, where it divides into two considerable branches, one for the integuments of the thumb, the other expands on the dorsum of the hand and supplies the index and middle fingers, and communicates with the dorsalis ulnaris nerve. The deep branch of the musculo-spiral nerve or the posterior inter-osseal nerve, [or ramus profundus dorsalis] winds backwards round the upper part of the radius and the supinator brevis, it then descends along the back part of the fore arm, with the posterior inter-osseal artery, and divides into several branches superficial and deep, which supply the two layers of extensor muscles. 9th. Circumflex or articular nene, arises from the lower part of the plexus, descends round the lower edge of the sub-scapular muscle, and passing backwards and outwards, leaves the axilla by a large opening between the humerus and the long head of the triceps, above the tendons of the latissimus dorsi and teres major muscles, and below the capsuiar ligament of the shoulder joint, it then winds round the neck of the humerus, attached to the internal surface of the deltoid ; in this course the nerve sends some small branches to the sub-scapular and the adjacent muscles^ it then divides into two branches, a superior and inferior, both of which encircle the neck of the humerus and send their numerous sub-di visions into the deltoid muscle. The DORSAL NERVES are twelve in number, the first pair passes between the two first dorsal vertebrae, and the last pair below the last dorsal vertebra, they also all divide into a posterior and an anterior or intercostal branch ; the pos- terior branches are small, pass backwards between the transverse processes, and supply the muscles and integu- ments of the back and loins ; of the anterior branches that of the first dorsal is largest, it rises above the neck of the first rib, and joins the last cervical nerve in the brachial plexus : the anterior branches of the second and third are smaller, they proceed backwards and outwards between 340 DUBLIN DISSECTOR. the corresponding ribs, and covered internally by the pleura; at the angle of each rib they pass between the intercostal muscles, run along the groove in the lower edge of each rib, supply the surrounding muscles, and op- posite the axilla each sends a filament across this cavity to the integuments on the inner and buck part of the arm; these filaments are named the nerves of Wrisberg, or the cutaneous nerves of the arm ; these two intercostal or spi- nal nerves then continue on in their course below the first and second ribs, and ultimately end in small cutaneous and muscular branches, which are lost on the lateral and forepart of the thorax ; the anterior or intercostal branches of the remaining nine dorsal nerves all pass in a similar manner between the ribs, and supply not only the inter- costal but also the adjacent muscles; the two last are chiefly distributed to the abdominal muscles and to the diaphragm ; the twelfth dorsal sends a branch close to the vertebrae to join the first lumbar ; all these anterior branch- es of the dorsal nerves opposite the neck of each rib are connected by one or two short branches to the ganglions of the sympathetic. LUMBAR NERVES ; of these there are five pair, they are larger than the dorsal, like them they divide into posterior and anterior branches ; the posterior are distributed to the lumbar muscles ; the anterior branches unite with each other in the substance of the psoas [magnus muscle] and form the lumbar plexus; this long and somewhat triangular plexus is situated along the sides of the four inferior lum- bar vertebrae : it communicates above with the last dorsal and below with the first sacral, and divides into the follow- ing branches ; inguino-cutaneous, anterior crural, obturator and lumbo-saeral. The inguino-cutaneous are generally three in number ; they descend from the two first lumbar nerves, pass through the psoas, and descend behind the pe- ritonaeum ; the first or the external descends obliquely out- wards over the quadratus lumborum muscle and behind the kidney, to the middle of the crest of the ilium, it then sends several branches to the abdominal muscles, and di- vides into a cutaneous branch which passes to the integu- ments on the outer part of the thigh and into the external spermatic nerve which passes beneath the internal oblique muscle, attaches itself to the spermatic cord, and distributes its branches to the cremaster muscle and to the scrotum, in the male, or to the round ligament and labium, in the female ; the second, or the middle inguino-cutaneous, descends internal to the last, pierces the abdominal muscles close to the an- terior superior spine of the ilium, and is distributed to the skin on the outer part of the thigh ; the third* or internal in- DUBLIN DISSECTOR. 3^j guino-culaneous, descend internal to the last, and divides near Poupart's ligament into two branches; one accom- panies the supermatic vessels and is lost on the cord, the other follows the crural vessels and is lost in the integu- ments and glands of the groin. The anterior crural nerve arises in the lumbar plexus from the four superior nerves; it perforates the psoas, descends obliquely outwards along its external side, on the iliacus internus, covered by the iliac fascia, and passes beneath Poupart's ligament [at from a quarter to] half an inch external to the femoral artery ; it is then covered by the fascia lata, becomes flat and broad, and divides into two fasciculi, a superficial and a deep; the superficial separates into four or five long branches which pierce the fascia lata -and descend along the inner and forepart of the thigh to the knee, some of these accompany the saphena vein. [Of these branches the four principal are the cutaneus externus, the cutaneus medius, the cutaneus anterior, and the cutaneus internus. The first is distributed to the integuments over the vastus externus and rectus muscles, as far as the patella ; the second perforates the sartorius, near the inner edge of the rectus muscle, to the integuments over which it is distributed ; the third is internal to the last, crosses the sartorius below it, and is distributed to the integuments over the vastus internus as far as the patella ; the fourth is still more internal, and is distri- buted to the integuments over the adductor muscles, at the fore and inner part of the thigh, some of its filaments reach the knee.] The deep fasciculus is larger, it immediately divides into numerous muscular branches, which supply the muscles on the outer and forepart of the thigh; they are divided into the external and internal branches, the former supply the vastus externus, rectus, iliacus internus, and tensor vaginae muscles ; the internal supply the sartorius, vastus internus, and crurseus ; three or four accompany the femoral artery near to the knee ; two or three of these pass into the adjoin- ing muscles, and one, the internal saphenus nerve, continues to descend to the inner side of the knee between the ten- dons of the gracilis and sartorius ; it then becomes attached to the saphena vein, and twines round this vessel as far as the inner side of the foot ; in this course it gives i.u..ierous filaments to the integuments of the leg. The obturator nerve is smaller than the preceding, it arises chiefly from the third lumbar, it perforates the psoas, and descends obliquely in- wards along the inner side of that muscle to the obturator foramen, through the upper part of which it escapes into the groin, where it is covered by the pectinseus, and where it divides into its two branches an anterior and posterior, having previously sent some twigs to the obturator inter- nus; the anterior branch is lost in the adductor brevis, 29* 342 DUBLIN DISSECTOR. pectinseus, and vastus intermis, and communicates with the anterior crural; the posterior branch supplies the gracilis the adductor magnus, and longus. The lumbo-sacral nerve proceeds from the fourth and fifth lumbar nerves into the pelvis, and soon divides into two branches, the superior glutseal, and the communicating; the glutaal escapes through the upper part of the sciatic notch, and is distribu- ted to the glutseus medius and minimus muscles along with the branches of the glutseal artery ; the communicating branch joins the first of the following nerves in the sacral or sciatic plexus. The SACRAL NERVES are five pair, [sometimes six,] they divide within the spinal canal into their anterior and pos- terior branches, the latter, very small, pass through the posterior sacral holes and supply the muscles and integu- ments : the anterior branches are very large, particularly the three superior, the two last are much smaller ; these five nerves, with the branch from the last lumbar, form the sacral plexus, large and flat, placed on the sacrum and pyri- form 'muscle behind the rectum, and the other pelvic vis- cera, it sends off the following branches both internal and external ; the internal or pelvic are the ha?morrhoidal and vesical, and in the female the uterine and the vaginal ; the external branches are the inferior or lesser sciatic, the in- ferior glutseal. posterior cutaneous, pudic, and great sciatic or posterior crural. All these escape by the lower part of the great sciatic not-ch, below the pyriform muscle. The lucmorrhoidal, xesical, uterine and vaginal branches are all small nerves which arise from the upper part of the plexus, are entangled with accompanying vessels, and interlace with each other; they are distributed to the different pelvic viscera, as their names imply. The lesser sciatic nerve es- capes from the pelvis with the sciatic artery, it then passes downwards to the space between the tuber isr.hii and tro- chanter major, but nearer to the former, round which it twines, and at its lower part divides into two sets of branch- es, a superficial and a deep ; the former pass over the ham- string r.rjs'les with the posterior cutaneous nerve, and are lost in jViese muscles ; and the latter pass under the mus- cles ana ~are distributed to the quadratus femoris, upper part of the adductor magnus muscles, &c. and some go to the hip joint. The inferior glutccal nerve leaves the pelvis below ; ! he pyriform mu?cle, and divides at once into several branches, vhich nre principally distributed to the glutseus maximrs, some also pass to the perinaaum and to the inner side of the thigh. The posterior cutaneous nerve of the thigh arises in common with the preceding from the second and third sacral nerves, escapes from the pelvis below the py- DUBLIN DISSECTOR. 343 riform muscle, becomes cutaneous, and descends along the back part of the thigh and leg, and communicates with the cutaneous nerves in the latter region. The pudic nerve arises from the third and fourth sacral, passes through the great sciatic notch internal to the preceding; it then re-enters the pelvis by the lesser sciatic notch, and passing upwards and forwards along the internal surface of the tuber ischii towards the pubis, it divides into two branches, an inferior and superior; the inferior, [the long inferior pudendal nerve] ascends obliquely forwards and inwards along the ramus of the ischium to the perinasum, and is 'distributed to the muscles and integuments in that region, also to the scrotum ; the superior branch [the long superior pudendal nerve] continues its course along the ramus of the pubis nearly to the symphysis, it then passes forwards along the dorsum of the "penis, increases in size as it approaches the glans penis, in the subcutaneous cellular tissue of which it terminates ; in the female the inferior branch of the pudic nerve supplies the labium, the superior, the clitoris. The great sciatic or posterior crural nerve is the principal branch of the sacral plexus, and the largest nerve in the body ; it proceeds from the four superior sacral nerves, escapes from the pelvis below the pyriforrn muscle, some- times through it, it then descends along the back of tho thigh over the gemelli, quadratus, and adductor magnus as far as the ham, where it divides into the external and inter- nal popliteal nerves; in this course this nerve is covered superiorly by the glutseus maxirnus and the hamstring muscles, inferiorly by the fascia lata and the integuments. [The sciatic nerve sometimes comes out from the pelvis in two trunks, one of these emerges beneath the pyriform muscle, the other perforates the substance of that muscle-: they then descend sepa- rately, and one becomes the external, the other the internal popliteal nerve.] The sciatic nerve sends off several cutaneous and mus- cular branches, the latter supply the hamstring muscles, the gracilis, and the adductor magnus. The external pop- liteal, or the peronfcal nerve, descends obliquely outwards along with the biceps tendon to the external condyle of the femur, it then turns forwards through the peronreus longus, round the neck of the fibula, and divides into two branches, the musculo-cutaneous [or external peronreal] and anterior tibial ; the peronseal nerve, before it arrives at the head of the fibula, sends off two long branches, termed the peroneo-cutaneous nerves of the leg. [Of thesw, one, the internal peroneo-cntaneous, descends 'behind the gastroenemius muscle, to below the middle of the leg, when it unites 344 DUBLIN DISSECTOR. with the external saphenus, or communicans tibiae a branch of the posterior tibial. The other, the external peroneo-cutaneous, is distri- buted to the integuments along the fibula.] The musculo-cutaneous nerve descends between the pe- ronseus longus and extensor digitorum longus ; to these and to the short peronaei muscles it sends several muscular branches ; about the middle of the leg, it perforates the fascia, and a little above the outer malleolus it divides into the internal and external tarsal nerves or dorsal nerves of the foot ; the internal is distributed to the integuments of the first and second toes, and communicates with the inter- nal saphenus nerve and with the anterior tibial ; the exter- nal supplies the integuments on the three outer toes, and communicates with the internal branch and with the exter- nal saphenus nerve. The anterior tibial nerve descends ob- liquely forwards along with the anterior tibial artery be- tween the tibialis anticus and the extensor digitorum longus and extensor pollicis, which muscles it supplies; it also sends branches through the fascia to the integuments ; it then passes beneath the annular ligament of the tarsus, and runs to the inter-osseous muscle between the two first meta- tarsal bones ; on the foot it sends a large branch to the exten- sor digitorum brevis,. also several cutaneous and communi- cating filaments, and it terminates by supplying the first inter-osseal muscle and the integuments of the two internal toes ; in the first inter-osseal space a small branch commu- nicates with the plantar nerves. The internal popliteal or posterior tibial nerve is larger than the preceding ; it descends nearly vertically between the heads of the gastrocnemius and solreus muscles, and behind the articulation of the knee and the poplitoeus muscle ; it then descends obliquely inwards beneath the sola3us and on the tibialis posticus and flexor digitorum longus, to the arch beneath the heel and the internal ankle; it here divides into the internal and ex- ternal plantar nerves. In the ham a quantity of fat sepa- rates this nerve from the popliteal vessels ; below the knee it becomes more closely connected to them, lying super- ficial and a little to their inner or tibial side ; at the lower edge of the poplitseus it passes to the outer or fibular side of the posterior tibial artery, and descends in that relation to this vessel as far as the internal malleolar region. The posterior tibial nerve above the knee gives off a small nerve, the posterior or external saphenus; this descends along the back of the leg, at first covered by the fascia, afterwards it is subcutaneous ; it communicates superiorly with filaments from the cutaneous branch of the sciatic plexus and with the external cutaneous branches of the peronceal nerve ; about the middle of the leg it is increased in size [by uni- DUBLIN DISSECTOR. 345 ting with the internal peroneo -cutaneous nerve,] and ac- companies the external saphena vein to the external malle- olus, behind which it passes ; it then curves forwards along the outer edge of the foot, communicating with the external dorsal nerves of the foot, and supplying the integuments and muscles on the outer side of this region. In the ham, the posterior tibial nerve gives off several very large mus- cular branches to the gastrocnemius, sola3us, and plantaris ; and in its course down the leg several smaller branches to the deep-seated muscles ; it also sends numerous filaments around the artery ; some very small twigs pass through the inter-osseous space along with the anterior tibial artery and join the anterior tibial nerve. The internal plantar nerve is larger than the external ; it passes forwards along the inner side of the tarsus above the abductor pollicis, sends many branches to the plantar muscles and to the integuments, and arriving near the base of the great toe, divides into four digital branches ; the first runs along the tibial side of the first toe ; the second subdivides and supplies the oppos- ed sides of the first and second toes ; the third, in like man- ner, the second and third toes ; and the fourth the opposed sides of the third and fourth toes : these digital nerves also supply the lumbricales, and communicate with the dorsal nerves of the foot. The external plantar nerve passes for- wards and outwards above the flexor brevis to the fifth me- tatarsal bone, and divides into two branches ; one, the su- perficial, supplies the little toe and the outer side of the fourth ; the deep branch passes obliquely inwards across the metatarsus, and supplies the inter-ossei and the other deep plantar muscles. SECTION IIL DISSECTION OF THE GANGLIONIC SYSTEM, OR GREAT SYMPATHETIC NERVES. IN addition to the small ganglions already noticed in the description of the cerebral nerves, viz. the lenticular or ophthalmic, the spheno-palatine, or Meckel's, and the sub- maxillary, also the several ganglions on the spinal nerves, we find one continued chain of these bodies placed anterior to the vertebral column on either side of the median line ; these ganglions, on each side, are all connected to each other, and resemble a knotted cord ; this cord receives the name of the sympathetic nerve. 340 DUBLIN DISSECTOR. The SYMPATHETIC NERVES, therefore, are two in number ; they descend from the base of the cranium perpendicularly along the neck, placed on the rectus capitis and longus colli muscles, and behind the great vessels and nerves ; at the upper end of the chest each of these nerves is divided by the subclavian artery into several branches, which en- circle that vessel and unite below it in the thorax ; through this cavity they descend at first obliquely backwards and outwards along the heads of the ribs and covered by the pleura ; they then incline a little forwards, and pass behind the true ligamentum arcuatum into the abdomen ; through this region they descend obliquely outwards on the fore part of the lumbar vertebrae and between the psoas muscle and the crus of the diaphragm ; they then sink into the pelvis, keeping close to the sacrum, and descend along the anterior surface of this bone obliquely inwards ; near its inferior extremity, or on the first part of the coccyx, these nerves unite and terminate in a small ganglion named coc- cygeal ganglion or ganglion impar. The superior extrem- ity of each sympathetic nerve is connected by several fila- ments to several of the cerebral nerves ; some of these connexions have been improperly termed the origin of the sympathetic ; in their course along the spinal column each nerve regularly communicates with every pair of the spinal nerves, with each of the cervical nerves by one filament, and with each of the dorsal, lumbar, and sacral nerves by two ; the sympathetic nerves may either be considered as independent parts of the nervous system communicating by numerous branches with every portion of that system, or they may each be regarded as a nervous cord formed by the union of branches from all the spinal and from seve- ral of the cerebral nerves; the latter is probably the more correct view. The sympathetic nerves send otf numerous branches, which are chiefly destined to supply the heart and the coats of the great vessels and all the pelvic and abdominal viscera ; these branches arise from the ganglions on these nerves ; of these there are generally three in the neck ; in the back and loins they correspond with the num- ber of vertebrse in those regions, and in the pelvis there are three on each side and the coccygeal or impar ganglion below ; these ganglions and their branches must be next examined. The Cervical Ganglions are three, the superior, middle, and inferior ; the superior cervical ganglion is of an oval figure and reddish colour, extending from the first to the third cervical vertebra, placed on the rectus capitis anticus, behind the carotid artery and jugular vein, and internal to the eighth and ninth cerebral nerves ; this ganglion sends DUBLIN DISSECTOR. 347 off several branches, viz. superior, inferior, internal, exter- nal, and anterior ; the superior branches are two in num- ber; they ascend in the carotid canal to the cavernous sinus, and communicate with the sixth, and with the vidian branch of the fifth ; in this situation a plexus or rather a ganglion may be observed on the external surface of the artery ; fine soft reddish filaments pass from this cavernous or carotid ganglion to the several nerves which compose the orbital plexus, but particularly to the filament of the nasal division of the ophthalmic which is destined to the lenticu- lar ganglion, also to the Casserian ganglion of the fifth, and several continue attached to the carotid artery, and are lost on its cerebral branches and in the tissue of the brain, and its investing membrane. The inferior or descending branches of the superior ganglion are small filaments to join the laryngeal nerves and the vagus, the superior car- diac nerve, (to be described presently,) and the continued cord of the sympathetic itself. The internal branches unite with the pharyngeai plexus ; the external join the superior cervical nerves, and the anterior unite with branches of the vagus and the facial, and form a plexus around the carotid artery ; from this several branches ex- tend along the external carotid, and form plexuses around each of its principal branches, which are named accord- ingly. The middle cervical ganglion is sometimes wanting, [as often as once in three cases, according to Meckel ; Horner, however, has always found it, although sometimes very small.] It is smaller than the superior, of a triangular, often an irregular form, is situated behind the carotid near the curve of the inferior thyroid artery, opposite the fifth vertebra, and upon the longus colli muscle ; it sends off branches in different directions which communicate with the cervical nerves and with the vagus ; it also sends some filaments to join the cardiac nerves. The inferior cervical ganglion is of an irregular figure ; it frequently appears to consist of several small ganglions connected to each other by reddish filaments ; it is situated between the transverse process of the last cervical vertebra and the neck of the first rib, behind and on either side of the vertebral artery, and between the scalenus and longus colli muscles; fila- ments from it communicate with the phrenic nerve and with the brachial plexus ; several also encircle the subcla- vian artery and extend along that trunk and its several branches, particularly along the vertebral artery ; from it also the inferior cardiac nerves proceed. The student may next examine the cardiac nerves ; there are three on each side, they are named superior, middle, and inferior; the superior cardiac nerve, though very small, takes a long 348 DUBLIN DISSECTOR. course ; it arises by two or three filaments from the supe- rior cervical ganglion, descends along the side of the trachea behind the carotid artery to the chest ; in this course it communicates with the faryngeal nerves, with the vagus, and with the inferior and middle ganglions of the sympa- thetic ; there is sometimes a small ganglion upon it near the inferior thyroid artery ; at the lower part of the neck it passes behind the subclavian vein and over the arteria in nominata ; it here divides into several filaments ; some pass along the coats of that vessel to the aorta, others join the recurrent nerve and the middle and inferior cardiac nerves ; the superior cardiac nerve on the left side has a similar origin and course in the neck, but it enters the chest in a deeper situation than the nerve of the right side ; it de- scends between the left carotid and subclavian arteries, and arriving at the arch of the aorta, divides into branches, some of which pass behind that vessel and join the cardiac ganglion ; others unite with the cardiac nerves from the sympathetic, or from the vagus and recurrent. The middle cardiac nerve on the right side is generally the largest of the cardiac nerves ; on the left side it is sometimes wanting, the inferior in such a case will be of a greater size ; it arises by several filaments from the middle cervical ganglion or from the sympathetic nerve about the middle of the neck ; it descends either a single cord, or divided into several pa- rallel filaments behind and internal to the carotid, and en- ters the thorax anterior to the subclavian artery ; it here is joined by large branches from the vagus and recurrent nerves, it then descends obliquely inwards along the side of the arteria innominata, glides between the arch of the aorta and the division of the trachea, and terminates in the cardiac ganglion or plexus. On the left side the middle cardiac nerve sometimes arises from the inferior cervical ganglion ; it enters the chest along the subclavian artery, and either joins the inferior cardiac nerve or enters the car- diac plexus. The inferior cardiac nerve or nerves proceed from the inferior cervical ganglion, and on the right side descend along the arteria innominata to the arch of the aorto, round which they pass to its forepart, and terminate principally in the anterior cardiac plexus ; some branches pass between the aorta and pulmonary artery to the car- diac ganglion ; these inferior cardiac nerves communicate with the preceding, and with the vagus and its recurrent; they form an irregular network or plexus in their course to the aorta ; on the left side these nerves accompany the subclavian artery and partly join the middle cardiac nerve, and partly the cardiac plexus. The cardiac plexus is situated behind the ascending aorta DUBLIN DISSECTOR. 349 near its origin, and in front of the trachea and of the right pulmonary artery ; it consists of a plexus of nerves form- ed by the cardiac nerves from opposite sides, also by branches from the eighth pair and the recurrent nerves ; in the meshes of this plexus several small ganglions are en- closed, and to the aggregate of these the term cardiac gan- glion is applied ; this, which is of a greyish colour and ir- regular form, receives superiorly and laterally the middle cardiac nerves from each side, also some filaments from the superior cardiac, particularly on the left side, and also some from the inferior cardiac, particularly on the right side ; the greater portion of the right superior cardiac joins the middle cardiac before the latter arrives at the plexus, and the inferior is chiefly distributed on the fore part of the aorta to the anterior cardiac plexus. From the great car- diac plexus branches proceed in various directions ; some pass backwards, encircling the posterior coronary artery, and forming a plexus around it, and accompanying its branches into the substance of the heart, others pass for- wards round the aorta, from the anterior cardiac plexus on it and on the right pulmonary artery, and vena cava ; from this plexus branches descend over the right auricle, accom- pany the anterior coronary artery, and form plexuses around it and its several branches ; from this ganglion also numerous nerves descend on either side along the pulmo- nary vessels, and communicate with the pulmonary plexus ; on the left side these branches encircle the ductus arterio- sus. The sympathetic nerves in the thorax have twelve gan- glions on each side, sometimes only eleven, the last cervi- cal and first dorsal being then united ; each of the thoracic ganglions is small and triangular, the base towards the spine, the apex externally, covered by the pleura and placed on the heads of the ribs ; the first ganglion is the largest ; they all communicate by one or two branches, which ascend obliquely outwards, with the anterior or in- tercostal branch of the spinal nerves ; from the base or an- terior edge of each ganglion small branches pass forwards to the mediastinum, ramify on the aorta and adjacent ves- sels, and communicate with the pulmonary plexus. From the six inferior ganglions the splanchnic nerves arise ; these are two iu number on each side, the greater and lesser or upper and lower. The great splanchnic nerve arises by four or five distinct roots from the sixth, seventh, eighth, ninth, and tenth gan- glions, they descend obliquely forwards and unite on the tenth dorsal vertebra into one cord, which enters the abdo- men either along with the aorta or separated from it by a 30 350 DUBLIN DISSECTOR. fasciculus of the diaphragm ; each nerve then expands into the semilunar ganglion. The lesser splanchnic nerve arises by two roots from the tenth and eleventh ganglions, they unite on the side of the last dorsal vertebra ; this small nerve then enters the abdomen through the crus of the diaphragm external to the great splanchnic nerve, with which it communicates, and then ends [in two branches, one of which joins the great splanchnic nerve, while the other runs into the renal plexus.] In the abdomen we find the semilunar and the lumbar ganglions on the sympathetic nerve of each side ; the semi- lunar ganglion of each side is situated on the diaphragm, and partly on the aorta on either side of the cosliac axis, and above and behind the supra-renal capsule. These are the largest ganglions on the sympathetic, they communicate with each other by several filaments on which small gan- glions are placed ; this communication surrounds the coe- liac axis, and is termed the solar plexus ; this plexus is si- tuated behind the stomach, in front of the aorta and above the pancreas ; from it numerous nerves pass off in various directions ; these nerves accompany the blood vessels, and form plexuses around each, which are named according to their destination, hepatic, splenic, and gastric [or superior co- ronary ;] these plexuses communicate with the eighth pair ; from the solar plexus, branches descend in front of the aorta ; these subdivide at the renal and mesenteric arteries, accompany these vessels, form plexuses around each, which are named accordingly the renal, superior, and inferior me- senteric plexuses, into each of these, branches from the lum- bar ganglions enter. The lesser splanchnic nerve enters the renal plexus ; from which on each side descends the spermatic plexus, this in the male follows the spermatic ves- sels and supplies the testicle ; in the female it enters the pelvis and supplies the ovarium and uterus. From the in- ferior mesenteric plexus branches descend to the edge of the pelvis, unite with others from the lumbar ganglions, and form a plexus around the internal iliac or hypogast.ric artery and its pelvic branches ; this is termed the hypogas- tric plexus ; it is joined by numerous filaments from the lumbar and sacral ganglions of the sympathetic, and it communicates with the pelvic branches of the sacral plexus. The lumbar or abdominal ganglions of the sympathetic are five on each side, sometimes only four or three ; they are situated on the anterior and lateral parts of the bodies of the vertebrae internal to the psoas muscle, are of an oval figure, but smaller than the cervical ; each ganglion is connected by one or two communicating branches which pass through the psoas to the anterior branches of the spinal nerves ; DUBLIN DISSECTOR 351 from the fore part of each, several filaments pass in front of the aorta and assist in the formation of the different ab- dominal plexuses which are principally derived from the solar plexus. The sacral or pelvic ganglions are three or four in number on each side ; the first is oval, the remaining are of an ir- regular form : they each communicate with the sacral nerves and send filaments to the hypogastric and pelvic plexuses; from the last ganglion on each side a small branch passes inwards in front of the coccyx ; these branches unite in the middle line and form a small plexus ; sometimes a distinct ganglion (ganglion impar) is placed here : from the convexity of the arch which these branches form, filaments pass off to the coccygeei, levatores, and sphincter ani muscles. CHAPTER IV. ORGANS OF SENSE. UNDER this head may be placed the anatomy of the nose, or the organ of smell ; the tongue, or the organ of taste ; the eye, or the organ of vision ; and the ear, or the organ of hearing ; to these may be added the integuments or the organs of touch. SECTION I. ANATOMY OF THE NOSE. SEVERAL bones enter into the formation of this organ ; these are all covered by a very delicate periosteum, which is almost inseparably united to the highly sensible lining mucous membrane ; to the anterior part of the bones of the nose, the cartilages, which form the septum and alee nasi, are attached. The nose is bounded, superiorly, by the nasal, frontal, ethmoid and sphenoid bones ; the roof of the nose is arched, and has different aspects, the anterior Sart looks downwards and backwards, the middle perpen- icularly downwards, and the posterior part downwards and forwards ; the floor of the nose which is nearly hori- zontal, but with a slight inclination backwards, and con- cave in the transverse direction, is formed by the palatine 352 DUBLIN DISSECTOR. plates of the maxillary and palate bones; the nose is bounded on either side by the superior maxillary, unguis, spongy, ethmoid and palate bones, and by the internal pterygoid plates. It is divided into two symmetrical por- tions (the nares) by the septum, which is composed of the azygos plate of the sphenoid, the nasal lamella of the eth- moid, the vomer, the spines of the palate and maxillary bones, and by a cartilage ; the external wall of each naris is deeply grooved by three fossae or meatuses, the superior, middle, and inferior, these are situated between the spongy bones, the middle is the widest. The nasal or lachrymal duct opens into the anterior third of the inferior meatus ; the Eustachian tube opens behind, but on a level with the inferior spongy bone, and at the side of the septum anteri- orly may be observed the superior orifice of the anterior palatine canal, which, although a distinct opening superi- orly towards the cavity of the nose, yet inferiorly towards the mouth, forms with the one of the opposite side a com- mon foramen ; this communication, however, between the nose and mouth does not exist in the recent state in the human subject, but does so in some animals, and in these Jacobson has ascribed a peculiar office to it. Into the mid- dle meatus, the antrum maxillare opens by a small oblique slit, which looks backwards and inwards, and although in the dry bone it appears tolerably large, yet in the recent state it admits only a crow quill on account of the mucous membrane being thrown into a small fold which surrounds it: in front of this is a groove, named the infundibulum, which leads from the frontal sinus, into this groove the an- terior ethmoid cells open. Into the upper meatus, the poste- rior ethmoid cells and the sphenoid sinus open. Each naris opens posteriorly into the pharynx, above the velum, by an oblong oval opening ; these are separated from each other by the vomer, the internal pterygoid plates bound them externally, the sphenoid above and the palate bones below. To the anterior edge of each naris the cartilages compo- sing the alse nasi are attached, these are five in number, one in the centre, two at each side ; the central cartilage is triangular and vertical, attached superiorly and posteriorly to the bony septum, its anterior edge is thick and sub-cuta- neous, and attached on either side to the lateral cartilages ; the lateral cartilages are two, one superior and triangular, attached to bone, the other inferior, and irregularly curved, convex externally, and attached to the preceding and to the septum ; in the ate nasi small pieces of cartilage also may be noticed distinct from the larger cartilages. All the internal surface of the nose and of the sinuses communi- DUBLIN DISSECTOR. 353 eating with it, are lined by a soft, vascular, and highly sensible mucous membrane; this is the pituitary OT Schnei- derian membrane ; this mucous membrane is continuous an- teriorly with the integuments : it adheres to all the internal surface of the bones of the nose, lines the sinuses, is con- tinuous through the nasal duct with the membrana con- junctiva of each orbit ; round the lower extremity of each duct it forms a slight circular fold ; and posteriorly it is continuous with the membrane of the pharynx and Eus- tachian tubes; this membrane adheres in some places in- separably to the periosteum, so as to deserve the name of a fibro-mucous membrane, in others it is villous, very vas- cular, soft and thick as on the septum and turbinated bones, and in these situations it and the submucous tissue are loose, cellular, or spongy, and probably possess some of the pro- perties of erectile tissue : at the extremities of the latter it forms thick fleshy-looking folds or lips ; in the sinuses it is pale and thin ; it is constantly moistened with a mucous secretion, but mucous glands are not distinct in it. The olfactory or first pair of nerves are distributed to it on the septum and sethmoidal region in the form of numerous plexuses, it is also supplied very generally with branches from the ophthalmic and superior maxillary divisions of the fifth pair ; the first pair are generally believed to endow the superior portion of this membrane with its peculiar sense or power of smelling ; while its acute sense of touch depends on the fifth pair, the nerve of feeling for the head generally. Majendie, also, has recently made some exper- iments to prove that the branches of the fifth pair in the nose are very sensible to acid or pungent odours, in the same manner as the surface of the eye, and that so far they may be accessory to the function of this organ. [The arterial distribution upon the lining membrane of the nose, is derived from the palatine, spheno-palatine, und infra-orbital branches of the internal maxillary artery ; and from the anterior and posterior ethmoidal branches of the ophthalmic artery. The veins for the most part follow the course of the arteries. The septum of the nose is sometimes inclined to the one side or the other, so as to divide the nares very unequally ; sometimes the septum is deficient either in its bony or cartilaginous portion. In the museum of the college is a preparation, in which the anterior open, ing of the left naris, is very small, that of the right natural ; poste- riorly the nares are entirely cut off from the fauces, by a membrane, except on the right side, where there is an opening large enough to admit the end of the finger ; no uvula is to be seen, and the malfor- mation appears as though the velum had become adherent posteriorly, except at the opening referred to. A flexible bougie introduced into either of the anterior openings of the nose is easily carried down into the pharynx through the opening in the preternatural septum. This 30* 354 DUBLIN DISSECTOR. was probably a congenital malconformation, and it would have been a point of physiological interest, to have ascertained the condition of the sense of smell, but unfortunately it was a common dissecting room subject, and its history was unknown. Another deformity which sometimes exists, is a deficiency of the bony septum, between the nose, and the mouth, or the cleft palate ; this may occur either singly, or conjointly with hair lip; it may also be combined with a deficiency in the alveolar margin of the superior maxillary bone. There is a preparation in the college museum o r the head of a negro, about forty years of age, in which the three de fects above referred to were combined. In the first place there was a large hair lip, behind which was a fissure through the alveolar mar- gin of the maxillary bone, behind which again, was a cleft through the palatal processes of the maxillary and palate bones, the vomer being reflected to the left side so that the left nostril is entirely sepa- rated from the mouth, while the right nostril and mouth form one cavity. Congenital deformity of the external nose is rare, but loss of substance from disease, sometimes occurs, for the cure of which deformity the rhinoplastic or taliacotian operations have been per- formed successfully. The spongy bones of the nose are sometimes destroyed by secondary syphilis. The lining membrane is the seat of acute and chronic inflammation and of hemorrhage or epistaxis. This membrane is also the seat of polypes, which occur at all ages, but most commonly in adults, and old people: they are of two kinds, malignant, and non-malignant ; and are apt to recur after extirpa- tion ; they are also divided according to their structure, into gela- tinous, fibrous, and vascular.] SECTION II. ORGAN OF TASTE. THE organ af taste resides in the mucous membrane of the tongue; this membrane is spread over the muscular substance of the tongue, adheres closely to it, and presents a number of projections or papillae ; the tongue is very vascular and is supplied with six nerves ; the gustatory is distributed anteriorly and chiefly to the conical or erectile papillae, also to two of the salivary glands on each side ; the lingual to the inferior surface and to its muscular sub- stance; the glosso-pharyngeal to the muscular substance and mucous membrane at its base ; experiments have proved that the fifth nerve endows this organ with its pe- culiar sense, that of taste ; and that the lingual or ninth is its motor nerve ; the glosso-pharyngeal is probably a sen- tient nerve to the posterior part of the tongue, it may also DUBLIN DISSECTOR. 355 connect this organ in sympathy with the stomach and the respiratory organs : the form and structure of the tongue have been already described under the anatomy of the mouth and pharynx, (see p. 39.) SECTION III. ANATOMY OF THE EAR. THE parts composing this complicated organ may be di- vided into three classes ; the first includes the external ear, or the cartilages and meatus extemus ; the second the tympanum with the Eustachian tube, ossicula auris with their muscles and nerves, the mastoid cells, the pyramid, promontory, &c. ; the third, the labyrinth or internal ear, which includes the vestibule, semi-circular canals, cochlea, and meatus internus with the portio mollis. [The muscles of the ear are arranged in three groups, the first group consists of three muscles, situated on the side of the head, and acting upon the external ear, so as to move it upon the head, these muscles are well developed and very active in the inferior animals. The second group consists of five muscles, is situated upon the auri- cle itself, and acts upon its different parts, so as to separate or ap- proximate them ; the muscles of this group are also better developed, and more active in the inferior animals, than in man. The third group consists of three muscles, some say of four, which are situated in the internal ear, and act upon the small bones of the ear so as to render the membrana tympani tense or relaxed as the case may be. First Group, three Muscles. Superior Auris, or Attollens, Vide p. 6. Anterior Auris, or Attrahens, ) yi^ e p 7 Posterior Auris, or Retrahens, \ Second Group, five Muscles. Tragicus, 1 Anti-Tragicus, Helicis Major, }> Vide p. 356. Helicis Minor, Transversalis Auris, J Third Group, three Muscle* Stapedius, i Tensor Tympani, > Vide p. 358. Laxator Tympani, S The auricle is united to the side of the head by three ligaments 356 DUBLIN DISSECTOR. which lie directly behind the muscles, which move the auricle upon the head.] The external ear consists of the pinna or auricle and the meatus externus; the pinna is composed of a thin fibro- cartilaginous plate, curved in different directions, so as to present different eminences and depressions ; the convex edge which forms the outline of it is the helix, below this is a short semicircular fold, the anti-helix, this divides su- periorly into two crura ; the depression between these is the fossa navicularis; in front of the meatus is an eminence, the tragus, directed backwards over the meatus ; opposite to this is a slight projection ; the anti-tragus ; within these several eminences is a deep conical cavity, the concha, which leads to the meatus externus, below this, is the pen- dulous fold of the integuments, or the lobe of the ear ; these several eminences are supposed to be of use in protecting the internal parts, also in collecting and directing the sound towards the meatus. In some subjects pale muscular fibres may be found on these eminences, they have been named according to their situation, as distinct muscles, tragicus, anti-tragicus, major and minor helicis, and transversalis auris ; these fibres may have some power in approximating these cartilages, and thus deepening the concha, they are seldom marked in the human subject, but in the lower classes of animals they are strong and distinct. The mea- tus auditorius externus extends from the concha to the mem- brana tympani, first forwards, upwards, and inwards, then downwards and inwards ; it is therefore curved, or concave downwards, about an inch in length, one-half cartilagin- ous, the other osseous. [In consequence of which when wishing to examine the bottom of the ear, the external ear must be drawn upwards, and backwards ; the passage may also be distended in its cartilaginous portion by the use of the speculum auris ; this canal is three lines in diameter.] It is lined by the skin, beneath which are a number of ceruminous glands, it is also furnished with a number of fine hairs, which are longer and more obvious externally ; the cuticle is continued also over the membrana tympani, from which it readily separates. The middle ear consists of the tympanum and its appen- dages. The membrana tympani separates this cavity from the meatus externus, the latter must be cut vertically to expose this membrane ; it is placed obliquely, its lower edge being more internal than the upper, or" nearer the median line, it therefore looks downwards, outwards, and forwards; it is concave towards the meatus, convex to- wards the tympanum, being drawn in the latter direction DUBLIN DISSECTOR. 357 by its connexion to the handle of the malleus ; it consists of three layers, an external or cuticular, an internal or mucous, and a middle or fibrous, which is dry and elastic. [On which in the elephant, Sir E. Home, found radiated muscular fibres.] The cavity of the tympanum may be seen either by divid- ing the membrane just described, or without injuring the latter, the roof of the cavity may be broken or cut through at the lower and internal part of the squamous plate ; this cavity is placed between the meatus externus and the la- byrinth ; it is of an irregular figure, rather circular ; it presents on its internal side or wall a tubercular eminence, named the promontory, and two foramina, one above, the other below that eminence ; the superior foramen, orfenes- tra ovalis, is closed by a membrane, to which the base of the stapes bone is attached, this opening communicates with the vestibule; the inferior or the foramen rotundum is also closed by a membrane, it communicates with the in- ternal part of the cochlea or the scala tympani ; the pos- terior wall of the tympanum presents superiorly the open- ing of a short canal, which leads to the mastoid cells, in this opening the short leg of the incus rests ; these cells are of irregular form and differ in different subjects ; beneath this is the pyramid, a small bony projection, hollow, con- taining the muscle of the stapes ; beneath the pyramid is the small foramen leading from the aqueduct of Fallopius, and transmitting the corda tympani. The tympanum pre- sents anteriorly the openings of two canals, one superior containing the tensor tympani muscle, the other, the infe- rior, is the Eustachian tube; this descends obliquely for- wards and inwards, and terminates by a trumpet-shaped mouth, behind the posterior nares, on a level with the infe- rior spongy bone ; this canal is small, and osseous poste- riorly, anteriorly it is large and formed of membrane ex- ternally, and of a curved fibro-cartilage internally. [It runs for six or eight lines in the petrous portion of the temporal bone, its entire length being about two inches, and its diameter a line and a half.] It is lined by mucous membrane, which is prolonged from the pharynx into the tympanum ; through this tube the at- mosphere can pass from the fauces into the tympanum, to support the latter on its internal surfaces In the superior boundary or wall of the tympanum are some small fora- mina for the passage of blood-vessels ; its inferior boun- dary presents the glenoid fissure, through which pass the corda tympani, the tendon of the laxator tympani, and the processus gracilis of the malleus. Within the cavity of 358 DUBLIN DISSECTOR. the tympanum are four small bones, first the malleus, at- tached to the membrana tympani, and resting on the se- cond, the incus, one leg of which is connected to the third, the orbicular, which is articulated to the fourth, the stapes, which rests on the membrane of the fenestra ovalis, be* tween which and the membrana tympani these bones form a connecting chain or spring, for the purpose of conveying the impressions of sound from the membrana tympani to the internal ear. The malleus is immediately behind the membrana tympani, it presents a head, neck, handle, a long and short process ; the head is smooth and articulated be- hind with the incus, the neck is small, and gives origin an- teriorly to the processus gracilis, which is about half an inch long, traverses the glenoid fissure, and gives attach- ment to the tendon of the laxator tympani muscle; the handle descends from the neck, adheres to the membrana tympani, and has a short process superiorly for the inser- tion of the tensor tympani muscle. The incus is internal and posterior to the malleus, presents a body, and a long and short crus ; the body is directed forwards and upwards, and receives the head of the malleus, the superior crus is short, and lies in the foramen of the mastoid cells, the in- ferior long, and perpendicular, is articulated with the fol- lowing ; The os orbiculare, extremely small, is between the incus and the following bone. [In the adult subject it is very frequently fused into the incus, this sometimes occurs even in children.] The stapes is placed horizontally, the base is on the fe- nestra ovalis, the head is articulated to the orbicular bone, the neck gives attachment to the stapedius muscle, the crura of the stirrup are separated by a space filled by membrane. [There is a diarthrodial joint between the malleus and incus ; but the other bones are connected by ligamentous tissue only.] There are three muscles in the tympanum, viz. stapedius, tensor, and laxator tympani. Stapedius arises within the pyramid ; its tendon is inserted into the neck of the stapes ; its use is to raise the stapes, and to press its base against the fenestra ovalis. Tensor tympani arises in the canal in the petrous bone above the Eustachian tube, passes backwards into the tympanum, and is inserted into the short process below the neck of the malleus ; use to draw the malleus into the tympanum, and thus to increase the concavity of the membrana tympani. Laxator tympani arises from the spinous process of the sphenoid bone, and from the Eusta- chian tube, ends in a delicate tendon which passes through the glenoid fissure along with the corda tympani, and is in- DUBLIN DISSECTOR. 359 serted into the processus gracilis of the malleus or the pro- cess of Raw. Use, to draw the malleus forwards, and thus to relax the membra na tympani. The labyrinth, or the internal ear, consists of the vestibu- lum, cochlea, semicircular canals, and meatus internus, the cochlea is anterior, the canals are posterior. Vestibulum is a small elliptical cavity behind the cochlea and in front of the semicircular canals, the fenestra ovalis opens on its ex- ternal side, the five orifices of the semicircular canals open superiorly and posteriorly, one opening from the cochlea is anteriorly, and posteriorly is the orifice of a small canal called the aqueduct of the vestibule, which opens on the posterior surface of the petrous bone, in a small cavity lined by dura mater, behind the meatus auditorius internus, and thus forms a communication between this cavity and the base of the cranium. A delicate but vascular mem- brane lines this cavity ; it is filled by a peculiar fluid, and extends into the aqueduct of the vestibule. The semicircu- lar canals are three in number, superior, posterior, and ho- rizontal ; the two first are vertical. [Their diameter internally is half a line and that extremity of each, which is nearest the foramina ovale and rotundum, is enlarged, so as to constitute what is called the ampulla.] They are surrounded by the petrous bone in front of the mastoid cells and behind the vestibule ; the superior and posterior are joined by one end ; there are, therefore, but five orifices of these canals in the vestibule ; each of these tubes is lined by a vascular membrane filled with a fluid which communicates with that in the vestibule. The coch- lea is in the anterior part of the petrous bone, is is some- what conical, the base towards the meatus internus, the apex towards the carotid artery ; the cochlea, internally, consists of a central pillar placed somewhat horizontally, named the modiolus, and of a spiral tube passing round this axis, two turns and a half; this tube is divided into two by a thin osseous and membranous plate, called lamina spiralis, and the two tubes are the scala? of the cochlea ; near the apex of the cochlea these scala3 communicate; near the base they separate ; one, the scala vestibuli, com- municates with the vestibule; the other, the scala tympani, with the tympanum through the fenestra rotunda ; the mo- diolus is hollow and expanded towards the apex ; this ex- pansion is called the infundibulum ; a branch of the audi- tory nerve passes through this cavity ; the aqueduct of the cochlea terminates in a small slit-like opening on the infe- rior surface of the petrous bone, just before the foramen lacerum posterius. The portio mollis of the seventh pair of nerves descends along the meatus auditorius internus, di- 360 DUBLIN DISSECTOR. vides into several fine branches, which are distributed to the membrane lining the vestibule, cochlea, and semicircu- lar canals. [The external ear is sometimes entirely wanting, sometimes the lobule alone is wanting, or it may exist, but adhere to the side of the head ; the auditory canal is sometimes imperforate, sometimes ob structed by morbid growths, of which the polypus is most common. The membrane tympani is the seat of acute and chronic inflamma- tion, which may go on to suppuration, ulceration, and the discharge of the bones of the ear, causing incurable deafness ; these bones are sometimes wanting at birth. The custachian tube is liable to congeni- tal imperforation, or to accidental obstruction from various causes, the result is deafness, more or less complete. An instrument has been introduced into the pharyngeal extremity of this tube, for the purpose of clearing away obstructions ; or to act on the principle of a bougie, dilating the passage, and thus curing deafness, by admit- ting air to the internal ear. Deafness is often caused, particularly in elderly persons, by an accumulation of wax upon the outer surface of the membrana tympani, and filling up the external passage. This is to be relieved by throwing in oil or tepid water so as to soften the wax, after which it may be readily removed. The nerves of the ear are the auditory or portio mollis, the facial or portio dura, and the chorda tympani. The arteries of the ear, both external and internal, are derived principally from the posterior auricular, internal maxillary, and temporal branches, of the external carotid.] SECTION IV. ANATOMY OF THE EYE. UNDER this head we shall examine not only the globe of the eye but its appendages ; these are the eyelids, the lach- rymal apparatus, and the muscles of the orbit : we shall commence with the latter. The muscles of the orbit are seven in number, viz. the levator palpebrae superioris, the obliquus superior and in- ferior, and the four recti ; to obtain a satisfactory view of these muscles, the roof and a considerable portion of the external side of the orbit must be removed ; then the peri- osteum having been divided, the first muscle appears. [The muscles which act upon the eye and its appendages, are eleven in number, and may be arranged in two groups, the one acting upon the appendages, and formed by five muscles, the other acting upon the ball of the eye itself, and formed by six muscles. DUBLIN DISSECTOR. 361 First Group, five Muscles. Occipito Frontalis, Corrugator Supercilii, Levator Palpebrse Superioris, } Vide p. 361. Orbicularis Palpebrarurn, Tensor Tarsi, Second Group, six Muscles. Superior Rectus, or Levator Oculi, } Inferior Rectus, or Depressor Oculi, ( Internal Rectus, or Adductor Oculi, f External Rectus, or Abductor Oculi, ) Obliquus Superior, ) Obliqu us Inferior, \ The muscles of the first group are situated on the head, face, and in part, in the orbit : those of the second group are entirely within the orbit.] LEVATOR PALPEBRSE SUPERIORIS is the highest and longest muscle in the orbit ; it arises narrow and tendinous from the upper edge of the foramen opticum, passes forwards and outwards beneath the frontal nerve, and becoming broader, aends down in front of the eye ; it then ends in a dense cellular expansion which is inserted into the superior border of the tarsal cartilage and into the superior pal pebral sinus of the conjunctiva behind the palpebral ligament. Use, to elevate and retract into the orbit the upper eyelid. OBLIQUUS SUPERIOR, at the upper and inner part of the orbit, arises on the inner side of the preceding, passes for- wards along the os planum, ends in a round tendon which plays through the fibre-cartilaginous pulley which is at- tached to the inner angle of the os frontis ; this tendon is then reflected backwards, outwards, and downwards, be- tween the superior rectus and the eye, and then becoming broad and thin, is inserted into the sclerotic coat between the superior and external recti, about midway between the en- trance of the nerve and the insertion of the superior rec- tus. Use, to draw the eye forwards and inwards, also to rotate it, so as to direct the cornea downwards, and accord- ing to some, inwards towards the tip of the nose : other au- thors consider it a rotator outwards. OBLIQUUS INFERIOR is situated at the inferior and anterior part of the orbit ; it arises tendinous from the orbital edge of the superior maxillary bone above the infra-orbital fo- ramen, and external to the lachrymal sac ; it ascends ob- liquely outwards and backwards below the inferior rectus, and is inserted by a tendinous expansion into the sclerotic coat behind the transverse axis of the eye, and between the sclerotic coat and the external rectus. Use, to draw the globe forwards and inwards, and to rotate it upwards and 31 362 DUBLIN DISSECTOR. outwards : the rotatory powers of the oblique muscles arc involved in some obscurity, but no doubt exists as to their principal use, that of drawing forward the globe, so as to oppose the retracting influence of the recti. Recti muscles are four in number, the superior is called attollens oculi, the inferior depressor oculi, the internal adduc- tor, and the external abductor oculi : they all arise from the periosteum around the optic foramen ; the external has an additional attachment to the foramen lacerum ; they all pass forwards around the optic nerve, separated from it by the ciliary vessels and nerves, and by a great quantity of fat ; a little beyond the middle of the eye they become ten- dinous, and are each inserted [into the sclerotic coat,] about a quarter of an inch behind the cornea ; the four tendons are connected together by an aponeurosis which is attached to the conjunctiva ; the use of these muscles is, collectively, to retract the eye into the orbit, and individually to move it, as their names imply. Under the head of lachrymal apparatus we may consi- der the lachrymal gland, membrana conjunctiva, palpebrae, and lachrymal passages. The lachrymal gland is placed in the upper part of the orbit, behind the external angular process of the os frontis, above the external rectus and the conjunctiva ; of a flattened oval figure. [It is of a light pink color ; it is convex above, concave below, and measures in length about ten lines, in breadth six lines, and at its thickest part two lines.] It is separable into two or more lobes, which, like other conglomerate glands, can be separated into numerous gra- nules ; these are united by a loose capsule ; from these, five or six small ducts proceed and open behind the upper eye- lid along the line of reflection of the conjunctiva from the palpebra to the sclerotic. The Membrana Conjunctiva is a mucous membrane lining each palpebra, and continuous at their margins with the in- teguments, it also covers the anterior part of the globe ; near the inner canthus it is thrown into a semilunar fold, [the plica semilunaris,] and is continued through the puncta lachrymalia into the nasal sac and duct, and becomes con- tinous with the mucous membrane of the nose. This membrane is more vascular on the palpebrasandcaruncula than on the surface of the eye ; it is loosely connected to the sclerotic coat to within half an inch of the cornea, it then becomes so delicate and so adherent that it. is difficult to separate it further, and although it is generally described as being continued over the cornea, it is impossible to dis- sect it from it unless previously macerated or changed by DUBLIN DISSECTOR. 363 disease ; at the inner canthus of the orbit it is thrown for- wards by a fleshy looking tubercle of a conical figure, the caruncuia lachrymalis, this is composed of a few mucous fol- licles and the bulbs of some fine hairs that project from its surface. The conjunctiva is a secreting, and according to some, an absorbing surface ; it is constantly moistened by the fluid it secretes, and occasionally by the lachrymal se- cretion ; it serves, as its name implies, to join the eyelids to the eye, to facilitate the motions of the former, and thereby to clear the surface of the latter ; it also closes the orbit against any extraneous substance, and serves to support and confine the eyeball in its several motions. Palpebrcc. are composed of the skin, the orbicular muscle, a thin cartilage connected to the base of the orbit by a cel- lulo-ligamentous connexion, and lined by conjunctiva ; in the superior there is also the expansion of the levator pal- pebrse muscle; the upper is larger than the lower eyelid, therefore, when they are closed the former descends below the transverse axis of the eye, and the inferior ascends but little to meet it ; they are both concave posteriorly, adapt- ed to the surface of the eye, their margins are thick, and furnished anteriorly with the eyelashes, posteriorly with numerous mucous follicles ; their opposed edges are sloped off obliquely towards the eye, so that when the lids are closed a sort of triangular canal is formed, the base of which is the surface of the eye ; along this canal the tears are supposed by some to be directed inwards towards the puncta, others, however, deny that any such space can ex- ist, and affirm that the lachrymal secretion flows along each palpebral sinus, and is directed inwards by the action of the orbicular muscle ; the skin of each palpebra is thin, the sub-cutaneous cellular tissue very loose and reticular ; beneath this the orbicular muscle is expanded. (See p. 6.) [The meeting of the palpebra? externally and internally, forms the angles or canthi, which are connected to the adjacent margins of the orbit by the external and internal palpebral ligaments, the latter of which is nearly half an inch long, and is made tense by drawing the lids outwards ; it is the guide for the incision in the operation for fis- tula lachrymalis.] The tarsdl cartilages are thin elastic plates ; the superior is semikmar and larger than the inferior which is long, narrow and nearly straight. [The superior tarsus is six lines broad at its widest part, the centre ; the inferior is nearly uniformly two lines wide. These cartilages are of use in preserving the form of the lids, and oppose the orbicularis muscle, which would otherwise pucker up the lids like the mouth of a bag, when closed by a drawing string.] The ciliary margins are thick ; their orbital edges thin 364 DUBLIN DISSECTOR. and connected to the orbit by the palpebral ligaments which are a continuation of the periosteum; these liga- ments are stronger towards the temple, where they decus- sate and attach the cartilages at their external canthus or commissure ; the tendo oculi [or internal palpebral liga- ment] fixes them internally. Between each tarsal carti- lage and the conjunctiva are the Meibomian glands or folli- cles; these are of a white or yellow colour, are arranged in nearly parallel vertical rows, and are more numerous in the upper eyelid ; they secrete a thin sebaceous fluid, which is discharged by a row of small holes along the edge of each tarsus behind the cilia. The cilia arise from bulbs which are beneath the skin ; those of the upper eyelid are more numerous than those in the lower; both are curved, convex towards each other. [Overhanging the eye and placed upon the projection formed by the os fronlis, are those hairs called the super cilia or eye-brows, sepa- rated from each other usually in the median line, by a bare space the glabella.] The Puncta Lachrymalia are two small holes always open, directed backwards and outwards, opposite each other ; they meet when the lids are closed ; each is situated in a little cartilaginous projection, about two lines from the inner canthus ; each is the orifice of the small lachry- mal duct. [Each is a line in depth and meets the duct at a right angle, so that in introducing a probe, it is to enter the punctum vertically, then it is to be brought to a right angle to its first position, and carried along the duct about half an inch ; it is then again to be raised nearly parallel with its first position, after which it may be carried into the lachry- mal sac.] The Lachrymal duels extend from the puncta to the lachry- mal sac. [They are half an inch in length and a line in diameter.] The superior is longer and more curved than the infe- rior; the former is concave inferiorly ; the latter is nearly straight, a little concave upwards; they both open into the external part of the sac a little above its middle, sometimes by one and sometimes by distinct orifices, behind the ten- do oculi ; each duct is surrounded by a process of that tendon, and lined by mucous membrane. [The plica semilunaris is a valvular fold of the conjunctiva, at the angle of the eye and directly external to the caruncle, it is triangular in form, the apex being internal, and base external ; its base is some- times furnished with a small cartilage, more frequently in the negro according to Homer. The use of this fold, in the human subject, appears to be for the free abduction of the eye ; it is &!BO analagous DUBLIN DISSECTOR. 365 to the third eyelid of animals; in which the third eyelid, is in inverse ratio to the others, until as we descend in the scale, it entirely supplies their place.] The Lachrymal sac is a small oval pouch of mucous mem- brane, closed above and leading below into the nasal duct, it is situated in a fossa formed by the maxillary and unguis bones, covered by the skin, the tendo oculi,and some fleshy fibres of the orbicularis muscle, also by a strong fascia which is derived from that tendon and connected to the surrounding bony margin. A small muscle has been de- scribed by Mr. Homer as arising from the edge of the os unguis, and inserted into the lachrymal sac and ducts ; he conceives it to have the power of compressing the sac, and directing the ducts and their contents towards it ; it is not, however, in all subjects to be distinguished from the orbi- cular, which last can effect these purposes. The Nasal duct (about three-fourths of an inch in length in the recent state) descends from the sack obliquely back- wards and a little outwards, surrounded by the maxillary, unguis, and inferior spongy bones ; beneath the latter it opens by a small slit-like orifice, which is surrounded by a circular fold of mucous membrane which is sometimes so loose as to appear as a valve, into the lower meatus, about an inch from the anterior part of the naris; this duct is formed of mucous membrane only, and which is closely connected to the periosteum. The nerves and vessels of the orbit have been already examined. The nerves of the pal- pebrse are derived from the portio dura of the seventh, from the lachrymal, frontal, and nasal branches of the oph- thalmic, and from the infra-orbital branches of the fifth pair of nerves : the vessels are branches of the ophthalmic, temporal, and facial. DISSECTION OF THE GLOBE OF THE EYE. [The organs forming the ball of the eye, may be conveniently grouped as follows ; fi;st, thrt j c concentric lamina?, the sclerotic coat, choroid coat, and the retina : second, two vertical organs, or mem- brant's, the cornea and the iris: tin d. three humours, the aqueous humour, the crystallineltiiis, or humour, and the vitreous humour.} It will facilitate the student in learning the anatomy of the eye, to dissect this organ in some of the inferior ani- mals; almost every part of importance may be examined with equal advantage in the eye of the sheep, ox, or pig, as in that of the human subject ; many of the minute parts are even on a larger scale, and can be dissected with great- er ease : we also have it in our power in general to dissect the eyes of the inferior animals in a perfectly fresh state. The eye is situated at the anterior and internal part of 31* 366 DUBLIN DISSECTOR, the orbit, behind the conjunctiva, surrounded by muscles and fat, and connected posteriorly by the optic nerve ; the axes of the eyes are parallel to each other, therefore not so to those of the orbits; each eye is nearly spherical ; the antero-posterior axis, which is nearly an inch, being about one or two lines greater than the transverse or vertical axis; the cornea, which is a segment of a smaller sphere, and which forms about the anterior fifth of the globe, being superadded to the larger sphere, formed by the sclerotic ; this spherical form favours the motion of the eyeball. The eye is composed of fluids or humours enclosed in different tunics, the latter are the sclerotic, choroid and retina, the first is a fibrous, the second a vascular and the third a nervous coat ; the humours are the aqueous, crystalline and vitreous ; these are also enclosed in distinct capsules. TUNICA SCLEROTICA is a dense, opaque, fibrous membrane, extending from the optic nerve to the cornea ; the nerve perforates it about a line internal to its centre by a small conical aperture, which appears traversed by fibres, so as to present a cribriform appearance ; it is doubtful, how- ever, whether this indistinct appearance may not partly depend on the central vein and artery of the retina which accompany the nerve through this opening; the sheath of the optic nerve is continuous with the fibres of this mem- brane; the external surface of the sclerotic is rough and perforated by several holes ; anteriorly it receives the cor- nea, and is so intimately connected to it, that maceration alone can separate them ; both are sloped off obliquely as well as slightly grooved; the sclerotic overlaps the cornea. [This is sometimes the case, but at other times the cornea overlaps the sclerotic, and in other cases the margin of (he sclerotic is grooved, and the edge of the cornea is received into the groove, like the crys. tal of a watch inserted into the rim.] Their connexion is still further secured by the conjunc- tiva externally, and by the membrane of the aqueous hu- mour internally ; a vertical section of this tunic from be- hind forwards will shew its great thickness near the optic nerve, and its thinness in the centre [being one line thick in the former situation, and half a line in the latter;] ante- riorly it is again strengthened by the tendinous expansion of the recti muscles ; this expansion has been improperly called the tunica albuginea ; the sclerotic consists of fibres which run in every direction, but which do not form dis- tinct laminae ; its internal surface is smooth and glisten- ing ; the ciliary vessels and nerves run between it and the choroid; from this surface a fine serous-like lamina may be raised ; this is reflected on the choroid coat. DUBLIN DISSECTOR. 367 The cornea forms the anterior fifth of the eye ; it is near- ly circular, its transverse diameter being a little greater than its vertical ; it is very smooth and transparent, of a laminated, not a fibrous texture; some fine cellular tissue connects the laminae to each other ; the cornea is more thick and pulpy in the child than in the adult; it is cover- ed anteriorly by a fine and closely adhering membrane, which though generally considered a continuation of the conjunctiva, is very different from it in its structure and properties. [That this membrane is continuous with the conjunctiva, is proved by the fact that it comes off with the conjunctiva and epidermis of those animals which shed their skin, as the locust, snake, &,c. The lining membrane of the stomach and that of the uterus are different in their appearance, and in their secretion, yet both are considered as belonging to the mucous tissue.] The concave surface of the cornea is lined by a fine elas- tic membrane, which is described by some as a part of the membrane of the aqueous humour ; it is, however, a mem- brane sui generis ; it is best seen in the eye of a horse, which has been macerated for some days, the external la- minse, which are now opaque, can be peeled off, leaving behind it this elastic cornea, which preserves its proper curve and transparency ; if it be cut it will curl upon itself, thus exhibiting true elastic cartilaginous properties. Fix the eye in a small shallow vessel, which can be immersed occasionally under water, carefully raise a small portion of the sclerotic, pass in some air between it and the choroid, these membranes can thus be easily separated ; then dissect off the sclerotic, this tunic can be readily detached as far as the cornea, here it adheres to the ciliary ligament; this connexion may be separated with the handle'of the knife, the cornea, or one-half of it, may also be removed with the sclerotic and the next tunic of the eye will be exposed, the choroid, with its appendages, the ciliary ligament, ciliary processes, and iris. The Choroid coat extends from the optic nerve all round the eye, between the sclerotic and retina, as far as the cili- ary ligament, where it appears on the external surface to terminate, but when a portion of it is raised, its internal surface will be found to extend inwards, in the form of folds or processes, termed ciliary, to be examined presently ; the external surface of the choroid is smooth, and loosely connected to the sclerotic by the ciliary vessels and nerves, and by fine cellular tissue; this surface is generally tinged by the pigment which transudes through it ; on this layer of the choroid, numerous fine vascular ramifications run- ning in parallel arches may be observed, these are con- 368 DUBLIN DISSECTOR. nected chiefly with the veins and are termed the vasa vor- ticosa : raise a portion of the choroid, by tearing it from the retina with a forceps ; its internal surface is covered by a brown pigment, which is thicker before than behind ; for a small distance round the optic nerve it is deficient ; wash off this pigment, the choroid will be found, if previ- ously injected, to be very vascular and villous ; this, the internal layer, which by dissection can be separated from the external, is termed membrana Ruyschiana ; the ciliary ar- teries supply this coat with blood, for the purpose of se- creting the pigment, which has the effect of absorbing all rays of light which strike the sides of the retina ; the optic nerve passes through a round opening in this membrane, the edges of which are not connected to the nerve ; this tunic is more dense anteriorly than posteriorly. The Ciliary Ligament corresponds to the junction of the iris to the choroid, and of the cornea to the sclerotic ; it forms a ring of grey colour, about two lines broad, of a soft and cellular texture, and has some resemblance to a nervous ganglion. The Ciliary Processes are sixty or seventy small triangu- lar folds of the choroid coat, which are arranged in a ra- diated manner around the lens on the forepart of the vi- treous humour, each extends inwards and backwards from the ciliary ligament as far as the border of the lens ; each of these processes, as well as the interstices between them, are covered by the pigmentum nigrum, the term corona ci- liaris is applied to this part ; the anterior edge of each pro- cess is connected to the ciliary ligament and iris, the pos- terior to the vitreous humour, and the internal is loose, and forms the circumference of the posterior chamber of the eye. The Iris is a delicate circular membrane, floating in the aqueous humour and suspended vertically behind the cor- nea, so as to divide the space between this and the lens into two chambers, an anterior and a posterior, the former is the larger of the two ; these chambers communicate through the central aperture in the iris, the pupil: this aperture is a little nearer its nasal than its temporal side ; the external border of the iris is fixed to the ciliary ligament, its poste- rior surface is also in part attached to the same and to the ciliary processes ; this surface is covered by pigment, and is named uxea ; the anterior surface is covered by the fine membrane of the aqueous humour, and streaked with dif- ferent coloured lines, some of which take a radiated course from the circumference towards the pupil, near which they cross, divide, and unite again, and appear to form or to end DUBLIN DISSECTOR. 369 in a fasciculus of circular fibres, which bound the pupil, and which are of a darker tint. [The anterior surface of the iris, is said to exhibit, one of two colors, light blue or orange, and the particular hue of the eye varies, accord, ing, as one or the other of these two colors predominates, and is corn, bined with the darker color of the pigment, on the posterior surface of the organ.] The iris, when examined with a magnifying glass, has a villous appearance ; when the pigment is washed otf the posterior surface, the fibrous structure is evident there also, and bristles may even be passed beneath some of the fasci- culi ; the iris is supplied with numerous arteries and nerves ; the former are branches of the long and anterior ciliary, the latter are derived from the lenticular ganglion, and from the nasal nerve ; it is not generally agreed on wheth- er the fibrous appearance of the iris depends on the pecu- liar arrangement of its vessels and nerves, or whether it possesses a true muscular structure ; its functions may lead one to incline to the latter opinion, as the pupil has the power of contracting rapidly when a strong light ap- proaches the eye, and of again dilating when the light is weak ; the use, therefore, of the iris is to regulate the quan- tity of light which is to enter the eye. The pupil is closed in the foetus by a delicate but vascular membrane, the membrana pupillaris ; this membrane is ruptured either at, or a short time previous to birth. [This membrane does not disappear until some days after birth in certain of the inferior animals.] The Retina may be best exposed by gently tearing off the choroid, (the eye being held under water,) and then placing an inverted glass globe, filled with clear diluted spirits, over the dissection ; the retina will become slight- ly opaque, and have a magnified appearance. The optic nerve having pierced the choroid coat ends in this thin and delicate membrane, which is transparent in the very recent eye, but soon becomes opaque after death ; the retina ex- tends around the sides and forepart of the vitreous humour without adhering to it, as far forwards as within two lines of the lens ; here the nervous matter ends by an abrupt line, along which a small blood-vessel runs. The retina is divisible into three layers : first, lamina serosa ; second, lamina nervosa; and third, lamina vasculosa. The exter- nal or serous layer is extremely delicate, it may be separ- ated by gentle pressure with the handle of the knife under water. This membrane was discovered by Dr. Jacob. The middle, or the nervous layer, is soft and grey, and continu- ous with the optic nerve ; the internal or vascular layer is 370 DUBLIN DISSECTOR. very delicate ; it lies on the vitreous humour, and is con- tinued on its forepart to the capsule of the lens, where it becomes adherent to the hyaloid membrane. Dissect off the posterior half of the retina from the vitreous humour, or cut transversely a fresh eye, and allow the humours to fall out, then look on the concave surface of the retina, and we may observe in the centre of the optic nerve a small dark point, the poms options ; this is the central artery of the retina, which then spreads its branches in the internal layer of the retina ; about two lines external to this, and in the axis of the eye, is a small yellow or orange spot, the punc- tum aureum, or spot of Soemmerring ; the retina is thrown into folds around this ; some describe a perforation and de- ficiency of the retina at this spot, it rather appears, how- ever, to depend on some peculiar organization. The hu- mours of the eye are the aqueous, cystalline, and vitreous. The aqueous humour is perfectly colourless, about five grains in quantity ; it fills the anterior and posterior cham- bers, the former about two lines, the latter about half a line in depth. This fluid is supposed to be secreted by a fine membrane, which is continued from the cornea over the iris, and through its pupillary margin to its posterior sur- face ; in the human eye, however, it is impossible to trace any such membrane through this extent. This fluid sup- ports the cornea and the iris, the latter can float and move freely in a fluid of such thin consistence. [This fluid is readily regenerated after having been lost, as in the operation for cataract.] The cystalline humour is a transparent double convex lens, a little more prominent behind than before, imbedded in the forepart of the vitreous humour behind the anterior third of the eye, and a little nearer to its nasal than its temporal side. Its axis corresponds to that of the pupil : it is surrounded by a fine capsule, which is thin and soft posteriorly, but anteriorly dense, and peculiarly elastic ; a small quantity of fluid (liquor Morgagni) is contained be- tween the lens and its capsule ; the lens is retained in its place by the hyaloid membrane, which splits into two la- minse at its border; these lamina pass, one before, the other behind it, and become connected to the proper cap- sule ; a small triangular canal (canal of Petit) is enclosed between these layers, the base is formed by the circumfer- ence of the lens. This canal is intersected by fine septa, it therefore presents a cellular or vesicular appearance when distended by air or injection. Some describe this canal as formed by the divison of the lamina vasculosa into two layers. The lens is soft and pulpy extcrnallv. DUBLIN DISSECTOR. 371 more dense towards the centre, or a little internal to that point ; maceration or boiling causes it to separate into wedge or triangular shaped pieces, the apices towards the centre ; each piece appears composed of successive plates, and each plate has a fibrous structure. In the foetus the lens is reddish and very soft ; in the adult it is transparent, and in the old it has an amber or yellowish cast towards the centre : the capsule of the crystalline lens receives some fine vessels from the central artery of the retina. The lens refracts the rays of light, and causes them to converge to a focus on the retina. The vitreous humour fills the two posterior thirds of the globe of the eye, it is thin and almost watery, but being enclosed in a fine membrane, it has a gelatinous consis- tence ; this membrane is called hyaloid, it encloses the fluid, and sends processes into it, so as to divide the whole mass into numerous cells, which communicate so freely that air injected will rapidly distend them ; or if one or two open- ings be made in this capsule, the whole of the fluid will gradually escape ; anteriorly the crystalline lens is con- nected to this humour by the hyaloid membrane separating into two laminae ; external to the lens, the ciliary process- es and the intervening pigment mark it in a striated man- ner, like the disk of a flower; this appearance, there- fore, has been called the ciliary disk, or corona ciliaris : the vitreous humour serves to support and expand the reti- na, and the other tunics of the eye, also, in transmitting the rays of light from the lens, it prevents their too rapid convergence, and thus causes an image of larger size to be painted on the retina. SECTION V. OF THE SKIN. THE integument of the body is composed of one continu- ed membrane, which is very dense, at the same time very extensible ; at the several orifices, it is continuous with the mucous membranes, a vascular line alone marks the dis- tinction between them : by maceration or putrefaction the skin may be divided into three laminae, the cuticle, rete mucosum, and cutis vera. The cuticle or epidermis is the external layer, it is dry, thin, 372 DUBLIN DISSECTOR. and transparent, and destitute of nerves and vessels ; it is most intimately connected to the cutis by numerous fine hairs which pass through it, also by the several exhalant and absorbent vessels that open on its surface by very minute pores ; in some situations it is very dense and opaque as in the hands and feet ; it is continued as a very fine pellicle into the different orifices, and can be traced for a considerable distance on the mucous membranes, thus, from the lips it extends over the pharynx and along the oesopha- gus as far as the cardiac orifice of the stomach, where it terminates in a firnbriated margin ; from the external ear it extends along the meatus externus, and covers the mem- brana tympani; inferiorly also it is continued along the mucous lining of the urethra, vagina, and rectum; the cuticle serves to defend certain parts of the body from pressure, to protect its surface from contact, and to prevent evaporation. The rete mucosum is a very thin, soft, vascular lamina, adhering to the cutis, connected to it by vessels, it has a villous appearance, and is tinged with a mucous fluid, which presents different shades of colour in different situations and in different individuals ; the peculiar complexion or colour of the body depends upon this secretion : in the negro, it is very thick and black, while the cuticle is transparent, and the cutis vascular and red ; some anatomists divide the rete mucosum into two, and some even into three or four laminae. The cutis vera, dermis, or chorion, is much more dense than either of the preceding laminae, it is very tough and strong, in some situations more so than in others ; its internal sur- face is cellular, its external is smooth and very vascular, [and is sometimes spoken of as a distinct lamina, under the name of the corpus or rete vasculosum :] it is also highly sensible, particularly in some situations, as in the fingers and toes, where numerous nerves are distributed to it in the form of small conical or oval papillae ; these are very dis- tinct at the end of each finger, they are very vascular, and into each a nervous filament can be traced, in these papil- lae the sense of touch more particularly resides. Although this sense resides more exquisitely in these particular situa- tions, yet many other parts of the body possess more or less of sensibility to the contact of foreign bodies, as well as to heat and cold : the skin generally is endowed with this faculty, also the voluntary muscles", the mucous sur- faces too, as far as we are acquainted with them, possess it, and some as the conjunctiva, the membrane of the nose, mouth, fauces, larynx, &c. even in a more eminent degree DUBLIN DISSECTOR 373 than the surface of the body ; the lining membrane of the rectum, urethra, vagina, &c. are all sensible to touch as well as to heat and cold. The sense of touch, as possessed by the voluntary muscles and by the integuments of the trunk and extremities, depends on the posterior or the gan- glionic roots of the spinal nerves; that of the head, face, eyes, nose, mouth, &c. on the ganglion ic portion of the fifth pair of cerebral nerves, and that of the pharynx, stomach, larynx, &c. on the glosso-pharyngeal and the vagi; the sensibility of the gen i to-urinary surfaces most probably depend on their supply of spinal nerves. How far the abdominal mucous surface, below the stomach, enjoys sen- sibility to touch is uncertain, most probably it possesses it only in a very faint degree, and this would lead to the question, are the branches of the sympathetic, sentient nerves? The greater portion of the alimentary canal being supplied from this source, and not being endowed with touch, would induce us to give a negative answer to this quere. The cellular membrane is connected to the deep surface of the cutis, which is itself cellular ; the sub-cutaneous cel- lular tissue is considered by some as a part of the integu- ments, and no doubt it serves as an additional covering to the body ; this tissue is, however, extensively distributed throughout the system, it enters into the composition of every solid, it forms the basis of the osseous and muscular systems, it also serves to connect some parts together, to separate others, and to confine all within their appointed limits. In some parts of the body, particularly those ex- posed to pressure, the cells of the cellular membrane are filled with adeps, in other situations, where the parts are subject to motion, the cells are very loose, and only contain a fine serous exhalation as in the eyelids and on the aspect of expansion of the joints ; the former species of cellular membrane has been named adipose, membrane [or adipo-cel- lular tissue,] the latter reticular membrane. [Or sero-cellular, being so named from the character of their respec- tive secretions : they co.exist in an inverse ratio, and the former does not exist, in those situations where the presence of fat would interfere with the functions of the organs, as in the eye lids, the organs of generation, the brain, &c.] In children the former abounds towards the surface and is in small quantity in the cavities ; in the old, on the con- trary, there is so little adeps beneath the skin, that the out- line of the muscles can be seen, and the vessels and other deeper seated parts can be distincly felt, whereas it is then 32 374 DUBLIN DISSECTOR. often found, even in emaciated subjects, in large quantity in the thoracic and abdominal cavities, in the former about the heart, in the latter in the omentum, around the kidneys, &c. ; there is never any adipose matter within the cranium at any age, although cellular membrane can be demonstra- ted even in the tissue of the brain. PART III CHAPTER I. ANATOMY OF THE VASCULAR SYSTEM. UNDER THIS HEAD WE MAY CONSIDER THE ANATOMY OF THE ARTK- RIES, VEINS, AND LYMPHATICS. SECTION I. ANATOMY OF THE ARTERIES. THE principal blood-vessels have been already described in the anatomy of the different regions ; in the present section the arteries shall be considered in a systematic manner, commencing with the aorta, and tracing its branch- es through all parts of the body. AORTA arises from the upper part of the left ventricle, op- posite the fourth or fifth dorsal vertebra, (see page 73,) as- cends obliquely forwards and to the right side, then turns backwards and to the left, and then descends along the dorsal vertebra? ; it thus forms the arch which terminates on the left side of the fourth vertebra : the thoracic aorta de- scends along the left side of the remaining dorsal vertebra), inclining a little to their forepart inferiorly, and passes be- tween the crura of the diaphragm : the abdominal aorta de- scends on the lumbar vertebrae, as far as the fourth or fifth, where it divides into the two common iliac arteries. The aorta is at first covered by the pericardium and the pulmo- nary artery ; as it ascends it lies between this vessel and the vena cava ; the arch lies on the trachea a little above its division, and on the bodies of the second and third ver- tebrae. In the posterior mediastinum the aorta descends on the left of the thoracic duct and vena azygos, and rather behind the oesophagus. In the abdomen it lies between the. 376 DUBLIN DISSECTOR. crura of the diaphragm and the psose muscles, on the left side of the vena cava and behind the vena porta, the pan- creas and the peritoneum. [Varieties. The aorta sometimes curves to the right instead of to the left, and this anomaly may or may not co-exist with a transposi- tion of the thoracic and abdominal viscera. The aorta has been seen to arise by a single trunk, which soon dividing, one branch passed in front of the trachea, the other behind it ; both then uniting to form the descending aorta. The aorta in many of the inferior mammalia, immediately after its origin, bifurcates, so as to form an ascending and a descending trunk, the former of which gives off the branches to the head, neck, and superior extremities, while the latter supplies the thorax, abdomino-pelvic cavity, and inferior extremities. This variety is peculiar to mammalia with long necks, and has been seen in the human subject. The aorta has been seen to divide into two trunks directly at its origin, its orifice being large and pre- senting five semilunar valves ; the two trunks curved upwards to the right and left, and meeting above, joined to form the descending aorta; each trunk gave off three branches, the subclavian, the exter- nal, and the internal carotids. The sweep of the arch of the aorta differs in different subjects, being in some the arc of a small and in others of a large circle. This artery usually enters the abdomen, op- posite the body of the twelfth dorsal vertebra, and terminates by bi- furcating over the inter-vertebral substance between the fourth and fifth lumbar vertebrse : this however may take place, either above or below the point designated. In addition to the anomalies of the aorta itself there are no less than twenty-five well authenticated varieties, in the origins of the branches coming off from its arch ; the descrip- tion and delineation of which are given by Tiedemann, and after him, but in a smaller and more accessible form by Knox. Most of these varieties will be referred to, in the description of the individual ves- sels ; many of them are analogous to the natural arrangement, in in- ferior animals. These anomalies may be arranged under the three heads, of community of origin, of multiplicity of origin, and of trans- position of origin. The number of branches coming off from the arch of the aorta, varies from two to six, but is most commonly three, being those named below, except the coronary arteries of the heart, which are not usually described as branches from the arch. The two varieties most frequently met with are, first, that in which the arteria innomi- nata, and the left carotid artery arise by a short common trunk ; .and second, that in which the left vertebral artery arises directly from the arch of the aorta, between the roots of the left carotid and subclavian arteries. There are in the college museum preparations of many of the arterial varieties ; several valuable preparations are also to bo found in the private collection of Dr. Alfred C. Post, of this -city.] From the arch of the aorta five arteries arise, the right and left coronary, the innominata, the left carotid, and left sub- clavian. The right and left coronary arteries arise above two of the DUBLIN DISSECTOR 377 sigmoid valves ; the right proceeds along the base towards the right side of the heart, divides into several long branch- es, which supply the parietes of the right auricle and ventricle, and communicate with the left coronary: the left descends obliquely along the left side of the heart sup- plying the parietes of the left auricle and ventricle, and communicating with the former around the base and apex of the heart. [Varieties. The coronary arteries sometimes arise by a large com. mon trunk which soon bifurcates ; sometimes there are three aud even four of these arteries, arising separately.] The arteria innominala arises from the upper part of the arch, ascends obliquely to the right side, in front of the trachea, and behind the sterno-thyroid muscle, and the left vena innominata ; opposite the sternal end of the clavicle it divides into the right subclavian and right carotid ar- teries. [Varieties. This artery though usually from an inch to an inch and a half in length, is occasionally two inches long. It is some- times double, that is, there are two trunks, coming off from the arch of the aorta, which bifurcate so as to form the subclavian, and coin- mon carotid arteries, of both sides. This artery, also called the brachio-cephalic, is sometimes entirely wanting, the subclavian and common carotid of the right side arising separately from the arch of the aorta. Small branches sometimes arise from the arch of the aorta, or from the arteria innominata, to be distributed upon the thymus body and muscles, at ihe lower part of the neck ; the inferior thyroid, and the internal mammary artery also sometimes arise from one or the other of the above mentioned trunks. The arteria innomi- nata has been ligatured by Dr. Mott, but the patient died of secon- dary hemorrhage after the lapse of three weeks.] The right and left [common or primitive] carotid arteries; the right arises from the arteria innominata, the left from the arch of the aorta; these vessels ascend obliquely outwards as high as the os hyoides, opposite which each divides into the internal and external ; in this course they are covered inferiorly by the sterno-mastoid, hyoid, and thyroid, and omo-hyoid muscles ; and superiorly, only by the skin, pla- tysma, and fascia ; the left is also covered inferiorly by the sternum and the vena innominata, and at its origin differs from the right in lying on the trachea, thoracic duct and oesophagus, but after this both ascend in front of the Ion- gus colli and rectus wapitis muscles, the inferior thyroid artery, and the recurrent and sympathetic nerves, and are enclosed in a sheath of cellular membrane, along with and to the. trucheal side of the vagus nerve and the internal ju- gular vein. [Varieties. The right common carotid is shorter than the left, by 378 DUBLIN DISSECTOR. the length of the innonainata, the two are however equal in calibre, and their calibre is proportionally greater in man than in the inferior animals, which is in accordance with the greater development of the cerebrum in the former. These vessels sometimes result from the bifurcation of two brachio-cephalic arteries, and at other times they arise by a common trunk, which comes off from the arch of the aorta and soon bifurcates ; in this case both subclavians arise directly from the arch, one on each side of the carotid trunk or else both of them to the left of that trunk ; in other cases both carotids arise directly from the arch between the two subclavians, or to the right of them, or even alternating with them. Again, the two carotids, arise from a trunk common to them, and the left subclavian ; and lastly, though most rarely, there is no common carotid artery, but the aorta being double, the external and internal carotids, arise directly from its two trunks. The left carotid artery not untrequently arises from the arteria innorninata. Usually, no branches are given off by the com- mon carotid, previous to its bifurcation yet this sometimes happens ; thus the inferior thyroid, a supernumerary thyroid called middle, the internal mammary, a Ihymus artery, have all been observed coming off from this trunk, and I have sevtral times seen one or more small branches distributed upon the sterno-cleido-rnasto-id muscle, from which circumstance they might be called the sterno-anastoid arteries. The point of bifurcation of the common carotid, is not invariable, it usually is opposite the upper edge of the thyroid cartilage, but I have a preparation, taken from a female, about twenty-rive years of age, in whom the bifurcation on the left, side look place opposite the infe- rior edge of the thyroid cartilage, and on the right side, opposite the middle of ihe same cartilage : in fact the bifurcation may take place at almost any point, between the origin of the artery, and its usual termination.] The external carotid artery ascends obliquely backwards to the forepart of the meatus auditorius, covered by the skin, platysma, and fascia, also by the lingual nerve, and digastric and stylo-hyoid muscles, the parotid gland and portiodura nerve : it lies superficial to the internal carotid, stylo-pharyngeus, and stylo-glossus muscles, the glosso- pharyngeal nerve, and part of the parotid gland ; it gives off the following arteries, anteriorly, the superior thyroid, lingual, and labial ; posteriorly, the muscular, auricular, and occipital ; superiorly, the pharyngeal, transverse fa- cial, temporal, and internal maxillary. [Variety. This artery may arise dir-ectly from the aorta, it is smaller than the internal carotid in the adult, and much smaller in the child, and is situated rather at the internal edge of that artery near ats origin ; it may come off from the common carotid, at any point between the origin of that vessel, and the superior margin of the thyroid cartilage.] The superior thyroid artery arises opposite the cornu of the thyroid cartilage, descends obliquely forwards and inwards beneath the sterno-thyroid, and omo-hyoid muscles, and J3TJBLIN DISSECTOR. 379 sends off the following branches -.first, the superficial, dis- tributed to the integuments and superficial muscles; se- cond, the laryngeal, accompanying the superior laryngeal nerve between the os hyoides and thyroid cartilage, and distributed to the muscles and mucous membrane of the larynx ; third, hyoidean, small and irregular, to the lower border of the os hyoides and adjacent muscles ; and fourth, superior thyroid, is distributed to the thyroid body. [Varieties. This artery is not urifrequently double, it may arise direotly at the bifurcation of the common carotid, or fairly from the common carotid ilself; from either point it may arise singly, or in common w.tii the lingual artery and in like manner from its normal point of origin ; the iaryngeal artery sometimes arises directly from the common carotid, and sometimes from the lingual arlery.] The lingual arlery arises immediately above the preced- ing, it ascends tortuously and obliquely forwards and in- wards, above the os hyoides to the base of the tongue, be- tween the hyo and the genio-hyo-glossi muscles, and then runs horizontally forwards towards the tip of the tongue; it gives off the following branches, first, hyoidean, small and irregular 4 second, dorsalis lingua, which ascends to the dorsum of the tongue, and is lost on the mucous membrane, near its base, also on the velum and fauces; third, suhlin- gual, passes forwards and outwards to the sublingual gland, mylo-hyoid muscle, and mucous mernbnme of the mouth ; and fourth, ranuie, which continues along the lingualis muscle to the tip of the tongue. [Varieties. This arteiy may arise by a common trunk, with either the superior thyroid, or the facial arlery : or it may be a branch of the former. The dorsal .artery of the tongue sometimes arises from the supeiior thyroid; and the s-isblingual artery, by a trunk common to itst-if and the submenlal, from the facial or labial artery- The branches of the lingual artery do not anastomose freely across the median line, in the subsfai.ce of the tongue, as has been already mentioned in the discription of that organ.] The labial [or facial,] or external maxillary artery arises op- posite the us hyoides, ascends obliquely forwards behind the digastric and between the submaxiilary gland and the base of the jaw, turns round the latter anterior to the m isseter muscle, and then ascends obliquely forwards and inwards towards the side of the nose ; in the neck it gives off, first, inferior palatine., which ascends along the side of the phar- ynx, and supplies the velum and the amygdala ; the branch to the latter often arises distinctly ; second, glandular to the sub-oiaxillary gland and adjoining lymphatic ganglia ; third, submental runs along the mylo-hyoid muscle to the chin, and supplies the surrounding muscles. On the face it gives off, fourth, inferior labial to the muscle and integu- 380 DUBLIN DISSECTOR. ments between the lip and the chin ; fifth, the inferior and superior coronary, these run along the border of the lips close to the mucous membrane and directly join those from the opposite side ; sixth, lateralis nasi to the muscles and skin on the side and dorsum of the nose ; and seventh, an- gularis, which communicates with the ophthalmic. [Varieties. This artery sometimes arises by a common trunk with the lingual; that of one side is very large, while that of the other side is very small; it terminates in the inferior or superior coronary artery, or the lateralis nasi, or it may be prolonged so as to form the frontal artery. The inferior labial, and inferior coronary arteries are in in- verse ratio to each other as to size, one of them being sometimes very small, in which case the other is proportionably larger than usual.] The muscular artery descends obliquely backwards, di- vides into several branches which are principally distri- buted to the sterno-mastoid muscle and to the surrounding cellular tissue and ganglia. The occipital artery arises opposite the labial, ascends ob- liquely backwards behind the digastric muscle, then curves horizontally backwards between the mastoid process and the atlas, and near the mesial line it ascends on the occi- put ; it gives off several muscular branches, some to the mastoid and trapezius muscles, several to the deep muscles on the side and back of the neck, and on the occiput it di- vides into tortuous branches, which ascend in different di- rections in the scalp, and inosculate with the different ar- teries in that region. [Varieties. This artery sometimes arises by a common trunk with the posterior auricular, or it may arise from the internal carotid ; it sometimes gives off the stylo-mastoid artery, which is normally a branch of the auricular, and enters the stylo-mastoid foramen, to be distributed upon the internal ear.] The posterior auricular artery arises above, often in com- mon with the occipital ; it ascends behind the parotid and between the meatus auditorius and the mastoid process ; it divides into several branches which are lost in the inte- guments of the ear and in the scalp. [Variety. This artery sometimes takes the place of the posterior branch of the superficial temporal artery on the side of the head.] The inferior or ascending pharyngeal artery arises near the division of the common carotid, ascends vertically to the base of the skull, and sends off several pharyngeal and palatine branches, and ends in a small branch [the poste- rior meningeal] that passes through the foramen lacerum posterius, and supplies the dura mater at the base of the cranium. DUBLIN DISSECTOR. 381 [Varieties. This artery is sometimes double, it may arise from the external carotid as usual, from the angle of bifurcation of the common carotid, from the internal carotid, from the occipital, or from the superior thyroid artery.] The transverse artery of the face arises from the carotid in the parotid gland, accompanies the duct of Steno, and is distributed to the muscles and integuments of the face, and joins the branches of the facial artery. [Variety. This artery is often a branch of the temporal, and its calibre is in inverse ratio to that of the facial, the place of which it sometimes supplies upon the upper lip and nose.] The temporal artery ascends through the parotid gland be- tween the meatus auditorius and the articulation of the maxilla, behind the zygoma, and divides on the temporal fascia into an anterior and posterior branch ; it gives off, 1st, branches to the gland; 2nd, anterior auricular; 3rd, the middle temporal; this pierces the fascia and is distributed to the temporal muscle ; 4th, the anterior or frontal supplies the skin and muscles of the forehead, and joins the ascending branches of the ophthalmic artery ; 5th, posterior temporal bends backwards and upwards in the scalp and inosculates with the occipital and auricular arteries. The internal maxillary artery ascends obliquely forwards behind the neck of the maxilla, between the pterygoid muscles, then between the external pterygoid and the tem- poral muscle ; it then bends down into the pterygo-maxil- jary fossa ; it gives oft' the following branches^ 1st, while internal to the neck of the maxilla, the middle artery of the dura mater; this ascends to the base of the cranium, passes through the spinous hole of the sphenoid bone, then runs outwards and forwards, and again ascends along the great wing of the sphenoid bone to the inferior angle of the pa- rietal, which bone it grooves very deeply ; it then ascends between this bone and the dura mater, divides into several branches, which ascend obliquely backwards, and are lost in the bone and the dura mater ; 2nd, the inferior dental arises opposite the last, descends obliquely forwards be- tween the bone and the internal lateral ligament, enters the dental foramen, and proceeds beneath the teeth, to the roots of which it sends very small arteries, and through the men- tal hole it sends a small branch to the muscles and mucous membrane, arid to inosculate with branches of the labial artery ; between the pterygoid muscles it sends off ; 3rd, the deep temporal branches, one posterior, the other anterior ; these supply the muscles and ascend close to the bone ; 4th, masseteric; 5th, pterygoid; 6th, buccal, to the buccinator muscle, the fat and integuments of the cheek ; 7th, superior dental, which winds round the maxillary tuberosity and 382 DUBLIN DISSECTOR. sends branches into the alveoli and to the gums; in the spheno-maxillary fossa it gives off; 8th, infra-orbital^ which passes along the canal of that name, is distributed to the muscles of the face, and communicates with the arteries of that region ; 9th, nasal passes inwards through the spheno- palatine hole, and is distributed to the mucous membrane on the spongy bones and on the septum ; 10th, the superior palatine descends along the posterior palatine canal, and is distributed to the muscles and to the mucous membrane of the palate, principally to the hard palate ; llth, the vidian; . this is a small branch which passes backwards, and takes the course of the first part of the vidian nerve ; these ter- minating branches of the internal maxillary artery are en- tangled with the divisions of the superior maxillary nerve. [The extensive distribution of the internal maxillary artery may be seen by the following enumeration of the organs supplied by it : viz. the superior and inferior maxillary bones, and the corresponding teeth, the muscles of mastication, the palatine arches, the soft paiale, and the pharynx ; the nasal cavities, the internal ear, the muscles and in. teguments of the face, and the bones of the cranium and the dura mater.] The internal carotid- artery ascends along the vertebral co- lumn and the side of the pharynx from the common caro- tid, posterior and external to the external carotid, behind the digastric and styloid muscles, internal to the jugular vein and anterior to the vagus and sympathetic nerves, to the foramen caroticum in the petrous bone ; it then bends tortuously forwards, upwards, and inwards, through the carotid canal accompanied by the superior branches of the sympathetic, enters the cavernous sinus, through which it makes two remarkable turns internal to the sixth pair of nerves, and arriving at the anterior clinoid process, it bends upwards and backwards, and a little outwards, and oppo- site the internal extremity of the fissure of Sylvius it di- vides into its three terminating branches, it first gives off the ophthalmic artery ; in the neck, and in the carotid canal, it sends small and unimportant branches to the surround- ing parts. [Variety. This artery, though rarely, may arise directly from the aorta, as when the latter vessel is double. The calibre of this artery is in direct ratio with the development of the cerebrum, and in the animal scale, it is in proportion to that of the external carotid, as the development of the brain is to that of the face.] The ophthalmic artery arises close to the anterior clinoid process, passes forward through the optic foramen, below the optic nerve and external to it; in the orbit it rises above this nerve and twines round it to the inner side of this cavity, along which it passes to the inner canthus DUBLIN DISSECTOR. 383 where it terminates ; while on the outer side of the optic nerve it sends off, 1st, centralis retina, which is very small, pierces the sheath of the optic nerve and passes along the centre of the latter, into the eye, where it divides into deli- cate ramifications ; these spread along the internal layer of the retina, and one or two pierce the vitreous humour, and extend to the capsule of the lens ; 2nd, the lachrymal passes along the external rectus muscle, and supplies the lachrymal gland, and the external part of the palpebrse : while above the optic nerve it gives off; 3rd, the supra- orbital, which passes forwards along the levator palpebrae, and through the superciliary notch, supplies the muscles and integuments of the eyebrow, and ascending on the forehead, divides into several branches, which are distri- buted to the scalp, and communicate with the temporal and occipital arteries ; 4th, the posterior ciliary, ten or twelve in number, very small, surround the optic nerve, and pierce the back part of the sclerotic ; pass between it and the choroid, and are distributed to the latter ; some of their branches continue as far as the ciliary processes and the iris ; 5th, long ciliary, one on each side ; they pass horizon- tally forwards, between the sclerotic and choroid mem- branes, as far as the ciliary circle ; here they divide, and form a circular inosculation round the circumference of the iris, from this several branches radiate inwards, and again unite in a circle near the pupil ; 6th, muscular arteries, to the different muscles in the orbit ; 7th, ethmoidal, passes through the posterior orbital foramen to the mucous mem- brane in the ethmoid cells ; 8th, superior and inferior palpe- bral, to the palpebrse, caruncula, conjunctiva, and lachry- mal sac ; 9th, nasal, passes beneath the trochlea, along the side of the nose, and inosculates with the labial artery ; 10th, frontal, ascends to the eyebrow and forehead. The posterior communicating artery arises from the carotid, opposite the ophthalmic ; passes backwards and inwards, external to the corpora rnamillaria, and joins the posterior cerebral artery ; this artery forms the lateral part of the circle of Willis ; it sends several branches to the surround- ing pia mater. [Variety. This artery is sometimes the largest branch of the in- ternal carotid, and then forms the principal origin of the posterior cerebral artery.] The anterior cerebral artery, or arteria calJosa, passes for- wards and inwards above the optic nerve; anastomoses with the opposite, by a short transverse branch, (the ante- rior communicating artery,) it then bends upwards and backwards round the corpus callosum, on which it termi- 384 DUBLIN DISSECTOR. nates by dividing into branches for the corresponding he- misphere of the cerebrum. [Variety. The anterior communicating artery, is usually of large calibre, and from one to two lines in length, but sometimes it is so short, that the two anterior cerebral arteries appear to be confounded at that point ; at other times its place is supplied by two smaller ar- teries.] The middle cerebral artery, very large, passes outwards in the fissure of Sylvius, and divides into two tortuous branch- es, which supply the anterior and middle lobes of the ce- rebrum. (See page 291.) The subclavian arteries; the right arises from the arteria innominata, and proceeds nearly transversely outwards, between the scaleni muscles, then obliquely downwards and outwards behind the clavicle ; it is covered at first by the sterno-mastoid, hyoid, and thyroid muscles ; by the in- ternal jugular vein, the vagus, and branches of the sympa- thetic nerve ; next, by the phrenic nerve and anterior sea- lenus muscle, and externally only by the skin, platysma, and fascia ; it first passes over the recurrent nerve, the lon- gus colli muscle, and sympathetic nerve ; next, the pleura and middle scalenus muscle, and lastly, the first rib. The left subclavian arises from the posterior part of the arch of the aorta, ascends nearly vertically out of the chest ; then turns outwards and downwards between the scaleni mus- cles, and over the first rib ; in the chest this artery lies very deep, and is covered by the pleura and the lung, also by the vena innominata, the vagus, the sternum, and the mus- cles attached to it ; it lies near the vertebrae, along the side of the oesophagus and thoracic duct ; in the rest of its course, its relations are similar to those of the right ; each sends off the following branches, vertebral, thyroid axis, internal mammary, superior intercostal, and deep cervical. [Varieties. Both subclavian arteries sometimes arise directly from the arch of the aorta, one on either side of the carotids, both to the left of the carotids, or alternating with the carotids ; the left subcla- vian may arise by a common trunk with the left carotid, forming a left arteria innominata ; the right subclavian sometimes arises from the left extremity of the arch, even as low as the fourth dorsal ver- tebra, and then turning to the right, passes behind the oesophagus or between it and the trachea, or even in front of the latter : (he right subclavian, is sometimes the second brancli from the arch, and passes behind the carotid of the same side ; the left snbclavian sometimes arises by a trunk common to itself and both of the carotids.] The vertebral arlery arises from the upper and back part of the subclavian : ascends behind the inferior thyroid ar- tery, enters the foramen in the transverse process of the fifth or sixth cervical vertebra, and ascends through the DUBLIN DISSECTOR. 385 several foramina in the superior vertebrse as high as the second ; it then bends backwards and outwards ; passes through the foramen in the transverse process of the atlas ; it then turns backwards aud inwards, round the articula- tion of this vertebra with the condyle, and pierces the dura mater; it then ascends obliquely inwards and forwards between the olivary and pyramidal bodies, and at the low- er edge of the pons it unites with the opposite, to form the basilar artery; in this course it gives small branches to the spinal nerves and to the inter-vertebral muscles ; at the foramen magnum it gives off, first and second, the posterior and anterior spinal arteries, which descend all along the spi- nal cord ; third, the inferior cereballar artery often arises from the basilar ; it runs tortuously around the medulla oblongata, below the vagus, and sends its numerous branch- es to the inferior surface of the cerebellum. [Varieties. The two vertebral arteries sometimes differ very much in their calibre, that of the left side being more frequently the largest ; these arteries usually enter the transverse foramina of the sixth cervi- cal vertebrae, but they may enter those of the fifth, fourth, third, or second. The left vertebral artery seems most subject to anomalies of which the most frequent is its origin from the arch of the aorta between the left carotid and the left subclavian ; it may also arise from the arch at the left of the subclavian ; or by two roots, one com- ing off from the aorta, as in the first variety, trie other from the left subclavian, and the two uniting at the fifth cervical vertebra ; or again, both roots may arise from the subclavian. Both vertebral ar- teries sometimes arise from the arch of the aorta, their relations to the other branches varying in different subjects. The right vertebral artery sometimes arises from the angle of the bifurcation of the arteria innominata. The anterior spinal arteries unite soon after their origin to form a single trunk, which is continued down the spinal canal.] The basilar artery, is formed by the confluence of the two vertebrals, it ascends in the median groove on the pons Varolii, sends small branches to the surrounding mem- brane, and at the upper edge of that body it divides into four branches, two for each side, first, the superior cerebellar artery, passes outwards and backwards, to the upper sur- face of each hemisphere of the cerebellum on which it spreads its branches ; second, the posterior cerebral artery, this receives the posterior branch of the internal carotid, bends backwards and outwards, and spreads its ramifica- tions on the posterior lobe of the cerebral hemisphere. (See page 351.) The thyroid axis, arises from the upper part of the sub- clavian close to the scalenus and phrenic nerve, it imme- diately divides into the four following branches : First, the inferior thyroid, ascends tortuously behind the common carotid, then bends downwards and inwards, sends branch- 33 386 DUBLIN DISSECTOR. es to the trachea, oesophagus, &c., and is distributed to the thyroid gland, in which it inosculates with the superior thyroid, and with the arteries of the opposite side ; second, the ascending cervical ascends along and is distributed to the anterior scalenus, longus colli, and rectus capitis anticus major muscles ; third, supra-scapular runs obliquely out- wards and downwards beneath the clavicle, passes above the notch in the superior costa of the scapula, supplies the supra-spinatus muscle, and descends beneath the acromion process to the infra-spinatus and teres minor muscles ; fourth, transversalis colli ascends obliquely outwards round the scaleni muscles, and beneath the trapezius, it divides into branches, one, the cervicalis superficialis, supplies the superficial muscles on the side and back part of the neck ; the other, the posterior scapular artery, -descends beneath the lavator anguli scapulae, and the rhomboid muscles along the base of the scapula as far as the inferior angle, where it inosculates with the subscapular artery ; the posterior artery of the scapula, as also the supra-scapular in many subjects, arise distinctly from the subclavian artery. [Varieties. The inferior thyroid artery may arise singly, or by a trunk common to itself and the supra-scapular, or the transversalis colli, or the internal mammary ; it may arise from the common caro- tid ; fronr the arteria innominata, or from the arch of the aorta, either between the innominata and the left carotid, or the left carotid and subclavian of the same side. When arising from either of the three last points, it is sometimes called the middle thyroid, and the usual inferior thyroids if existing, are but small branches, often not distri- buted at all upon the thyroid body. Sometimes there are two infe- rior thyroid arteries upon the one side or the other, one arising as usual, the other from the common carotid ; occasionally this artery arises on one side only, and bifurcates to form the right and left thy- roids. The supra-scapular artery sometimes arises in common with the inferior thyroid alone, or that and the transversalis colli, or some- times even in common with the internal mammary ; it may arise di- rectly from the subclavian itself, or even from the axillary artery ; in the latter case it is not so much exposed in ligaturing the subclavian behind the clavicle. The transversalis colli arises at different points, either to the inside of the scaleni muscles, between them, or more frequently on their outer side ; it may arise in common with the in- ferior thyroid, or the supra- scapular.] The internal mammary artery arises opposite the thyroid axis, it descends obliquely forwards and inwards, between the cartilages of the ribs and the pleura, as far as the ensi- form cartilage, it gives branches to the pleura, pericardium, and mediastinum, a long branch to the diaphragm, which accompanies the phrenic nerve, also intercostal branches, which inosculate with the aortic intercostals ; it terminates by sending branches to the diaphragm, and to the abdo- DUBLIN DISSECTOR. 387 minal muscles, the latter inosculate with the epigastric ar- tery. [Varieties. This artery on the right side, has been seen to arise from the arch of the aorta, and from the arteria innominata, it also sometimes arises in common with the inferior thyroid.] The superior intercostal artery arises between the scaleni, descends behind the pleura, in front of the neck of the first and second ribs, and supplies the two first pair of intercos- tal muscles. The cervicalis profunda arises opposite the last, ascends obliquely backwards and outwards, between the transverse processes of the sixth and seventh cervical vertebrae, and ascending on the back of the neck, supplies the complexus and the other deep muscles in that region, and inosculates with the descending branches of the occipital artery. [Variety. This artery sometimes arises in common with the supe- rior intercostal. Cruveilhier says, that it invariably passes backwards between the transverse process of the seventh cervical vertebra and the first rib, and not as described above.] The axilliary artery descends from the lower edge of the first rib, obliquely outwards to the tendon of the latissimus dorsi muscle, it is covered by the integuments, and at first by the external border of the great pectoral muscle, lower down by the great and lesser pectoral, and still lower down by the tendon of the great pectoral only ; it passes over the first intercostal, and serratus magnus muscles, the bra- chial plexus, the subscapular, and the tendons of the latis- simus dorsi and teres major muscles ; the axillary vein de- scends along its inner and anterior part, and the brachial plexus lies posterior and external to it ; it sends off the following arteries, the thoracica acromialis, the superior and long thoracic, the subscapular, the posterior and anterior circumflex. [Varieties. The anomalies of this artery principally affect the origin of the ulna, the radial, and the interosseous arteries ; the first of these is the one most commonly arising from the axillary, but sometimes all these come off from it simultaneously. This artery sometimes divides into two branches of equal size, of which one is muscular, and gives off some of the branches usually coming from the axillarv, while the other is the brachial artery. It sometimes bifurcates so as to form two brachial arteries which re-unite low down upon the arm.] The acromial thoracic artery arises from the front of the axillary below the subclavian muscle, above the lesser pec- toral, and opposite the fissure between the great pectoral and deltoid muscles ; it divides into several branches, which pass some to the pectoral muscles, others to the acromion process, deltoid muscle, and integuments of the 388 DUBLIN DISSECTOR. shoulder and arm, one long branch accompanies the cepha- lic vein, [the deltoid artery.] The superior thoracic artery arises a little below the pre- ceding, sometimes in common with it, it passes forwards and inwards, and divides into branches which supply the cellular membrane and ganglia in the axilla, the pectoral muscles, the breast, and the integuments. The long thoracic artery arises below the lesser pectoral, descends obliquely forwards, along the side of the chest, parallel to the lower edge of the great pectoral, to which it sends some branches, it terminates in the intercostal mus- cles and integuments, and inosculates with the internal mammary and the intercostal arteries. [Varieties. This artery sometimes arises in common with the two last, sometimes in common with the subscapular, whose place it in part supplies in other cases.] The subscapular artery arises opposite to and descends along the lower edge of the subscapular muscle, and soon divides into an anterior and posterior branch ; the former continues to descend along the back part of the axilla, and supplies the subscapular, serratus magnus, and latissimus dorsi muscles ; the latter passes backwards round the infe- rior costa of the scapula, behind the long tendon of the triceps ; and above the latissimus and teres major muscles, it is distributed on the dorsum of the scapula to the infra- spinatus and teres minor muscles, and inosculates with the supra-scapular artery. [Varieties. This artery may arise in common with the circum- flex, the long thoracic or the superior profound artery, and in the lat- ter case is as large or even larger than the brachial.] The posterior circumflex artery arises below the last, some- times in common with it, it passes out of the axilla between the long tendon of the triceps and the humerus, turns round this bone between it and the deltoid muscle, to which last it sends numerous branches. The anterior circumflex artery is smaller than the prece- ding, and arises either from it or from the axillary ; it passes outwards round the anterior part of the humerus, beneath the deltoid, coraco-brachialis, and biceps; to these muscles it sends its branches ; it also sends one long branch along the bicipital groove to the synovial membrane of the shoulder joint. The brachial artery descends obliquely outwards to the bend of the elbow, where it divides into the radial and ul- nar arteries ; it is covered by the skin and brachial aponeu- rosis, and inferiorly by the fascia of the biceps, and the median basilic vein ; it lies on the inner side of the coraco- DUBLIN DISSECTOR. 389 brachialis and biceps, and passes over the upper part of the triceps, the coraco-brachialis, and the brachialis anti- cus ; it is accompanied by a vein on either side, also by the median nerve, which above lies to its outer, and below to its inner side, it passes superficial to the artery about the mid- dle of the arm ; in addition to several muscular branches it sends off the superior and inferior profunda, and the anastomotica. [Varieties. The anomalies of this artery as of the axillary, have reference principally to the high origin of the radial or ulnar arteries. This high bifurcation of the brachial artery may take place at any point between the axilla and the bend of the elbow : the interosseous artery may also arise from the brachial. The high origin of the ulna, is most commonly from the axillary artery, and that of the radial from the brachial artery, and in either case the branch is more superficial in its course than when coming off at the usual point : these high origins may occur in both arms, but they appear to be most common in the right arm. The brachial artery is sometimes double, that is the axillary bifurcates, and the two trunks thus formed descend to the bend of the elbow, and re-uniting form a short trunk which then gives off the ulna and radial. In the private museum of Dr. Alfred C. Post of this city, there is a remarkable variety of this artery, on the left side: "just below the axilla it gives off a branch, which runs superficially down the anterior surface of the arm, and a little below the elbow, joins the trunk of the radial artery, which bends abruptly forward to receive it." These varieties of the brachial artery should be borne in mind, even in the common operation of venesection, as in these cases Ihere is danger of producing a traumatic aneurism, which accident has occurred.] The superior profunda arises below the teres major, ac- companies the musculo-spiral nerve obliquely downwards and outwards, between the three heads of the triceps, and in the musculo-spiral groove of the humerus; it divides into two large branches, one descends in the triceps to the olecranon, the other accompanies the radial nerve to the outer condyle, and communicates with the radial recurrent artery. [Varieties. This artery may arise from the subscapular or either of the circumflex branches of the axillary artery : it sometimes gives off the next artery.] The inferior profunda arises opposite the tendon of the coraco-brachialis, descends on the surface of the triceps, along with the ulnar nerve, to the inner condyle, and com- municates with the ulnar recurrent. The anastomotica arises about two inches above the joint, passes inwards, supplying the adjacent muscles, and inos- culating with tho preceding and with the ulnar recurrent arteries. 33* 390 DUBLIN DISSECTOR. [Variety. This artery sometimes arises immediately below the superior profunda.] In the triangular hollow at the bend of the elbow, the brachial artery divides into the radial and ulnar. The ulnar artery is the larger of the two, it descends along the ulnar side of the fore arm to the palm of the hand, covered superiorly by the superficial flexors and prona- tors, and by the median nerve ; inferiorly by the skin and fascia, overlapped, however, by the tendons of the flexor digitorum sublimis and flexor carpi ulnaris, between which it descends to the wrist ; it passes over the brachialis an- ticus, flexor profundus, pronator quadratus, the annular li- gament of the carpus, and the flexor tendons in the palm of the hand ; it is accompanied by two veins, and by the ulnar nerve, the latter descends along its ulnar side ; it gives off, first, the anterior ulnar recurrent, which ascends in front of the inner condyle, on the brachialis anticus, and inosculates with the anastomotica ; second, the posterior ulnar recurrent, large and tortuous, ascends behind the in- ner condyle, along with the ulnar nerve, aud anastomoses with the anastomotica and inferior profunda arteries ; third, inter-osseal artery, passes backwards and divides into an an- terior and posterior branch ; the anterior inter-osseal artery descends along the forepart of the inter-osseal membrane, beneath the deep flexors, pierces that membrane near the pronator quadratus, and descends on the back part of the carpus, and is distributed to the carpal bones, and to the sheaths of the extensor tendons ; the posterior inter-osseal artery passes backwards beneath the anconaus, and de- scends along the back of the fore arm, sending its branches to the extensor muscles ; this artery superiorly sends a very large recurrent branch in the anconseus muscle to the ole- cranon, to communicate with the superior profunda; fourth, muscular branches to the two layers of flexor muscles, and to the skin ; fifth, dorsalis carpi ulnaris turns round the lower end of the ulna, and spreads its branches on the back part of the wrist and hand ; sixth, superficial palmar, forms the palmar arch, bends obliquely across the palm of the hand towards the thumb, and inosculates with branches of the radial artery ; seventh, ramus profundus, passes beneath the flexor tendons, across the fifth and fourth metacarpal bones, and joins the deep palmar branch of the radial artery, and thus completes the deep palmar arch ; from the superficial arch long digital branches pass, these divide and supply the opposite sides of all the fingers, except the radial side of the index finger and the thumb. [Varieties. These may be arranged under two heads : first, varie- ties in the origin and course of the ulnar artery itself, and secondly, DUBLIN DISSECTOR. 391 varieties in the origin and distribution of its branches. First, the ulnar artery may arise from the brachial, but this is rare ; the point at which it comes off is usually about two inches above the bend of the elbow ; it much more frequently arises from the axilla- ry ; in either of the above cases after reaching the bend of the el- bow, it may take the usual course, but most commonly it is super- ficial in its whole extent, being placed either beneath the fascia of the arm and fore arm, or between it and the integuments. When the ulnar artery arises from the axillary, there is sometimes a large anastomotic trunk between it and the brachial artery. This artery may arise at the usual point, but run superficially down the fore arm. Secondly, varieties of the branches : the interosseal artery may arise from the radial, brachial, or even axillary arteries ; it also sometimes supplies the place of the radial artery, which is in that case very small. Its recurrent branch sometimes arises directly from the in- terosseal, and perforates the interosseal ligament at a different point from the parent trunk. Not unfrequently a branch arises either from the interosseal or the ulnar artery, which follows the course of the median nerve, passing into the palm of the hand either before or behind the annular liga- ment : from its relation to the median nerve, this artery has been called by Tiedemann and Cruveilhier, the median artery. It is often as large as the radial and ulnar arteries, and sometimes even it is very large, and supplies the place of those arteries which are then in a rudimentary state. It sometimes arises from the brachial artery. Its termination varies very much; in some cases it runs into the superficial palmer arch, in others it unites with the radial artery to supply the radial half of the palm of the hand ; and in still other cases, it takes the place of the radial, and supplies the radial half of the hand, while the ulnar artery supplies the ulnar half. A know- ledge of this artery is very important in a surgical point of view. There is great variety in the arrangement of the superficial palmar arch and the terminal branches of the ulnar artery. This artery is usually distributed to both sides of the little, ring, and middle fingers, and to the ulnar side of the fore finger ; sometimes, however, it is distributed to the ulnar half of the hand only, while the radial half is supplied by the radial or the median artery ; in other cases, the ulnar artery supplies both sides of the thumb, and all the fingers ; sometimes the superficial palmar arch is not joined by the superficial volar artery ; at other times there is no arch. There may be no anastomotic branch between the ulnar and the radial or median, or thfre may be one just at the lower edge of the annular ligament. The digital arteries sometimes arise from the deep palmar arch, of which there is a preparation in the valuable private collection of Dr. J. Kearny Rodgers, if this city, the whole of which collection has been deposited by him in the College Museum.] The radial artery continues in the direction of the brach- ial artery ; it passes along the radial side of the fore arm to the wrist, turns round the external lateral ligament of this joint, then passes forwards between the heads of the two first metacarpal bones into the palm of the hand, and 392 DUBLIN DISSECTOR. terminates in three branches ; in the fore arm it is covered by the skin and fascia only, lies between the supinator longus externally, and the pronator teres, and flexor carpi radialis internally; it passes over the biceps, supinator brevis, pronator teres, flexor digitorum sublimis, flexor pol- licis, and pronator quadratus ; it is accompanied by two veins, and the radial nerve is to its external side in the mid- dle of the fore arm ; on the outer side of the wrist it is co- vered by the extensor tendons of the thumb, and on the back of the hand by the skin and fascia ; it gives off, first, radial recurrent, large and tortuous, bends outwards and upwards along the supinators and extensors, to which it sends several branches, and inosculates with the superior profunda ; second, muscular branches to the flexors and su- pinators ; third, superficialis vol 7 8 of the ilia, - - ) Distance between the crisis of the ilia, - 8 3 Transverse diameter of the superior strait, 4 6 Oblique do. of do. - - 4 5 Antero-postefior do. of do. 4 Transverse diameter of the cavity, - - 4 In the Female. Inches. Lines. 9 4 5 4 5 4 4 4 8 Oblique do. of do. - 5 5 Aiitero-posterior , do. of do. - - 5 4 Transverse diameter of the lower strait or outlet 3045 Antero-posterior do. of do. - - 3 3 44 The latter may be increased to 5 inches, from the mobility of the coccyx. The ossa innominata are composed of two thin but com- pact laminae with an intervening diploe, the latter is nearly wanting in the iliac fossa, where the bone is transparent, as well as in the cotyioid cavity. In the foetus each os in- nominatum is developed from three points of ossification, one in the iliac fossa, one in the sciatic tubercle, and ono near the spine of the pubis ; these three soon unite in the cotyioid cavity. Some years after birth the iliac crest is developed as a distinct epiphysis, the sciatic tubercle and anterior inferior spine of the ilium are also covered by dis- tinct plates of bone, and in some the angle of the pubis; in some females also, a plate of bone or epiphysis consti- tutes the spine of the pubis, and occasionally grows so large and remains so moveable, as to resemble the rudi- ments of a marsupial bone. Jn .the fretus, the pelvis is very small and deep, and narrow transversely ; the true and false are nearly in the same perpendicular line, the acetabula are nearer the middle line and look more out* wards, they are not beneath the pelvis as in the adult* hence the thigh bones in the infant cannot support or balance the weight of the trunk. [The os innominatum is sometimes fractured by great external violence, and severe inflammation of the soft parts will ensue : some- times the bone is perforated at the bottom of the iliac fossa which is by some supposed to be natural, by others to result from absorption of the bone. The articulation at the symp!iy.- ". x (^ s %'?S ' -V v,- ,, , ,- ; ., ., , - : ..- ^', . ,- ... , - . B VM^ VR ^DRtt% VK %Hc %WWNI wWC VHfe MMMH^ ^ttlMl iWc ^BvNVlMlB %vRffVWllB VM^ , , \V ,t V \'- X V .' v . . ^^v tW!i$ tta bw^m w4 Hi ^1 H(g H^ rtv\i "*^ 1^ Iwt^ ^^ $IHMll vV^W^ tt$w ^5fc v\x w^x\ lv> tw< s ^1^4 K^ t^fe l*l*^t 1^ fc* ww^ \^r^\ vy WV$JIWA ^ *^h> >l *|J^' V ^ f*tt$ ; V * ' ^ V tv jNmfti /- A- - x ,- ; --v-- *i wlwrlw - v : v-.' - ^MttHnMilK ^'wv^tv^r t^vmv v\v.> A-'v-vKx, o.wov MM -- v. mA -vx- M Vv.-v X /V .' X '.' \ 1 "./ . ...... T. '.- ^ ,\ - . V-. ' - >>*- .jw.1uhr*.'" v *"V . tr ,^, ^ n tf^fc- > ^ i i ifc^S r n ^^" ^^- - - A^ .^^^. fc > ' . v \ .. v .- <\ . . \ i .v - - - - v ;- ; - -- -- -\ -- - x - -.i . vV**ft^ ' X1< ^ ' v v . DUBLIN DISSECTOR. 437 spine or process, which supports the nasal bones before, mid tnO ethmoid bone behind, on each side; of this is a groove Which forms part Of tho superior nasal fossa 1 . On i -ithcr side of the median line of the frontal hour, and proceed- ing from above downwards, we observe, first, a smooth surface, covered by the occipito-frontalis muscle ; second, the frontal eminence, which is particularly prominent in the young; beneath this is a slight depression, bounded below by the superciliary arch, towards the inner third of which is the supra-orbital hole, or notch, which is com- pleted into a hole by a ligament, and which transmits tho supra-orbital nerve and vessels; from this notch a small foramen leads obliquely into tin; diploe of tin: bone; im- mediately above the internal third of this arch is the pro- minence of the frontal sinus, and below it is the edge of the orbit, at each extremity of which are the angular pro- cesses; the external is prominent and joins the malar bone, the internal is thin and broad, covers some cells, and joins the unguis ; above and outside the external is the temporal ridge or process, which is prominent below and leads up- wards and backwards to join a similar ridge, on the parietal bone, this separates the forehead from the temple, and gives attachment to the temporal muscle and fascia. On the cerebral or internal surface of this portion of the frontal bone, we observe in the median line a groove; for the longitudinal sinus ; interiorly tin- edges of tins groove unite into a ridge to which the falx adheres, and which ex- tends down to a small hole, the foramen ca'cum, which is between this bone and the ethmoid ; on either side of this median lino are numerous irregularities, corresponding to the convolutions of the brain, in general, but, not uniformly, for occasionally a prominent part of the bone is opposed to an eminence of the brain ; these are named the marn- millary eminences, and the digital impressions, in some of the latter the bone is often very thin. The circumference of the os frontis is thick, rough, and serrated to join tho parietal bones; the tables are cut unequally, the internal being deficient above, the external below, so that it rest;* on or binds down the two parietal bones abov, and sup- ports or is overlapped by these below; below the temporal process it is bevelled otf thin arid rough, and is inserted under and between the laminae of the ala of the sphenoid bone. The inferior portion of the frontal bone presents the deep ethmoidal notch in the centre, in front of which is tho nasal spine and the orifices of the frontal sinuses, its edges are cellular to unite to and communicate with the colls of the ethmoid bone ; along its margins are two foramina, the anterior and posterior orbital, they arc common to this 37* 438 DUBLIN DISSECTOR. and to the ethmoid bone, the anterior transmits the nasal twig of the ophthalmic nerve and anterior ethmoidal ar- tery, the posterior, the posterior ethmoidal artery ; on cither side are the orbital processes, smooth, concave, and triangular, the apex behind presenting near the external angular process a deep pit for the lachrymal gland, and near the internal a slight depression for the cartilaginous pulley of the superior oblique muscle of the eye, instead of a depression there is sometimes a small spine ; the cere- bral surface of these processes is convex, but very uneven, marked by the brain and vessels ; their posterior margins are thin, and cut obliquely to support the lesser wings of the sphenoid bone. The processes of this bone, enume- rated by anatomists, are eleven, viz., two orbital, four an- gular, two superciliary, two temporal, and one nasal ; the foramina are nine, viz', one, the foramen coecum ; two and three, the frontal sinuses, between the nasal and internal angular processes ; four and five, the supra-orbital ; six and seven, the anterior; and eight and nine the posterior orbital ; these last, as well as the foramen coacum, are often common to this and the ethmoid bone. The os frontis is joined to four bones of the cranium, viz., the two parie- tal, the sphenoid and ethmoid, and to eight bones of the face, viz., the nasal, superior maxillary, lachrymal, and malar. The structure is thick towards the nasal protu- berance and superciliary ridges, but very thin in the or- bital plates ; it is composed of two compact laminae and an intervening diploe, by the absorption of the latter and the greater separation of the plates, the cavities called the frontal sinuses are formed ; these do not exist in childhood, and in the adult their extent is very variable ; they gene- rally extend from the ethmoid notch upwards and outwards for one-third of the superciliary arch, sometimes much further ; they are generally separated by a septum ; their use is not fully ascertained. This bone is developed from two points of ossification, one in each frontal prominence ; from this, ossification extends in rays which unite in the middle line, but occasionally a suture remains between them ; this has been said, but without sufficient foundation, to be more frequent in women than in men. [The os frontis is sometimes developed by three pieces, which arr distinct at the time of birth, the third piece being situated upon the. median line, ovoid in form, and separating the two lateral parts ; of this there is a specimen in the Museum. The frontal suture is rather rare, I have seen six or eight specimens of it. The frontal sinuses* sometimes spread over a large portion of the orbit, and one case is recorded in which they extended upwards and backwards, beyond the coronal or temporo-frontal suture ; they are lined with mucous DUBLIN DISSECTOR. 439 membrane, which is sometimes the seat of inflammation ; they com- municate with the anterior ethmoiclal cells. Muscles. Four pair arc attached to this bone ; three pair arise from it, the temporal from its temporal ridge and surface; the orbi- cularis palpebrarum and corrugalor supercilii from its internal angu- lar processes ; and the occipito frontalis is inserted into the integu- ments over its front and lower part.] The parietal bones are symmetrical, and form the upper and lateral parts of the cranium ; each is nearly square, convex and smooth externally, about the centre is the pro- tuberance, which is better marked in children, below this is the curved temporal ridge continuous with the pro- cess of that name on the os frontis, to this the temporal aponeurosis adheres ; below this it is rough for the attach- ment of the temporal muscle; of the four edges, the upper or perietal is the longest, it is serrated, and with the oppo- site bone forms the sagittal suture ; the anterior or frontal edge is also serrated to join the os frontis in the coronal suture; the posterior or occipital edge is very irregular, and joins the occipital bone in the lambdoid suture : in this suture small bones called ossa Wormii or triquetra are often found ; the inferior or temporal edge is the shortest, it is concave, and joins the temporal bone by the squamous suture ; of its four angles the anterior superior is nearly right, in the child this is deficient and the fontanelle exists ; the superior posterior angle is somewhat rounded; near this in general is a foramen [parietal] which transmits small vessels from the pericranium to the dura mater, the inferior anterior is long and curved, and joins the sphenoid bone, the inferior posterior is very irregular and joins the mastoid portion of the temporal bone : the cerebral surface is mark- ed by the convolutions of the brain, and by the branches of the middle artery of the dura mater; this vessel is in a groove, sometimes in a perfect canal or tube in the anterior inferior angle, and from this the branches pass upwards and backwards, a large one ascends a little posterior to the coronal edge ; along the parietal border is half a groove, which with that in the opposite bone, lodges the longitudi- nal sinus; and near this in the adult skull are irregular depressions for the glandular Pacchioni or the granulations of the dura mater ; the posterior inferior angle is grooved and lodges part of the lateral sinus : the structure of the perietal bone is similar to that of the frontal ; it is devel- oped from one point of ossification, which is in the parietal prominence; it is joined to five bones, viz. the frontal, sphenoid, temporal, occipital, and to its fellow. Muscles, One muscle only is attached to this bone, the temporal, 440 DUBLIN DISSECTOR. which arises from it ; the occipito-frontalis slides over it to some ex- tent.] The occipital bone is curved and of a rhomboidal figure, placed at the posterior and inferior part of the cranium ; it presents two surfaces, the external or posterior, or basi- lar, is convex, smooth above, presents near the centre the great protuberance to which the cervical ligament is connect- ed ; from each side ,of this leads the superior transverse ridge, to which the occipito-frontales, trapezii, and complex i muscles are attached ; midway between this and the fora- men magnum, is the inferior transverse ridge, to which the splenii, recti.majores and obliqui superiores are attached ; from the tuberosity a spine leads down vertically in the median line as far as the foramen magnum ; this latter is of an oval figure, and transmits the medulla spinalis, the vertebral vessels, and the sub-occipital nerves-; it is larger internally than externally, in .front of this is the -basilar process, which is very thick and strong, it passes forwards and a little upwards .into the base of the skull to join the sphenoid bone.; its sides are rough and contiguous to the petrous bones; it , is also rough inferiorly, for the attach- ment of muscles and the mucous membrane of the pharynx. Near the forepart of the foramen are the condyles, smooth and oblong, covered with cartilage, looking downwards, outwards, and backwards, and converging anteriorly ; their anterior and inner edges are the deepest, their long axis is from before backwards, in which direction, as also from side to side they are convex, they are uneven internally near their centre, for the insertion of the lateral ligaments from the odontoid process ; they are articulated to the atlas ; behind these is a fossa in which there is generally a small foramen through which a vein and small artery pass, and before them is another fossa in which there is always a foramen for the ninth pair of nerves, [the posterior and anterior condylaid foramina.'] External to each condyle is the jugular eminence, semilunar, bounding posteriorly the foramen lacerum posterius in the base of the cranium and giving attachment to the rectus lateralis muscle. The up- per angle is acute ;. -the edges very irregular as also along the sides ; ossa triquetra are often entangled in the notches. The internal or .cerebral surface is concave, and marked by two lines which cross about the centre, or opposite the tuberosity, these bound four fossce, the two superior receive the posterior lobes of the cerebrum, and are marked by their convolutions, the inferior are smooth, and lodge the hemis- pheres of the cerebellum, to the vertical ridge is attached the falx cerebri above and falx cerebelli below ; the lower extremity of the latter is bifurcated, the upper half is grooved for the longitudinal sinus; to the transverse ridge DUBLIN DISSECTOR. 441 the tentorium is attached, it is grooved for the lateral sinus ; the basilar process is concave from side to side, to support the pons Varolii and the basilar artery ; on either margin of it is a slight groove for the inferior petrosal sinus : on each side of the foramen magnum above the jugular pro- cesses is a groove for the lower extremity of the lateral sinus. This bone is joined to six bones, viz. the two parie- tal, two temporal, the sphenoid, and the atlas. Its process- es are six, namely, two condyles, two jugular, the basilar, and the tuberosity. Its foramina are five proper and two common ; the proper are, the magnum, the two anterior and two posterior condyloid ; the common are, the forami- na lacera postica basis cranii, these foramina are comple- ted by the petrous bone, each is imperfectly divided into two, a small anterior portion which transmits the eighth pair of nerves, and a large posterior one, or thimble-like fossa, which lodges the lateral sinus as it ends in the jugular vein. This is a very hard bone, although thin throughout except at the ridges and processes ; it is developed from four points, one for the basilar process, one for each con- dyle, and one for the upper and back part. [The whole of this bone above the superior transverse ridge is sometimes composed of three or four large ossa triquetra ; this bone and the sphenoid become inseperably united in the adult subject, which is also true of some inferior animals, hence the two are de- scribed as a single bone by some anatomists under the name of oa basilare ; the groove for the right lateral sinus is usually larger and deeper than that for the left, and sometimes it is continued almost vertically from the longitudinal sinus towards the foramen magnum, near which it diverges to reach the foramen lacerum posterius. Muscles- Thirteen pair are attached to this bone; two pair arise from it, the occipito-frontalis and trapezius from the superior trans- verse ridge ; eleven pair are inserted into it; the sterno-mastoid into the superior transverse ridge, the splenius capitis externally and the complexus internally into the space between the two transverse ridges ; recti capitis postici major and minor, and obliquus capitis su- perior, between the inferior transverse ridge and the foramen mag- num ; the rectus capitis lateralis into the jugular process; the recti capitis antici major and minor, and superior and middle constrictor muscles of the pharynx into the basilar process.] The temporal bones are situated at the lateral, middle, and inferior parts of the skull, of a very irregular shape, thin above and before, and thick behind and below ; each may be divided into three portions, the squamous, the mastoid, and the petrous. The pars squamosa is the superior divi- sion, it is flat, thin, and scaly, forms part of the temporal fossa, is bounded above by a semicircular edge, and below by the zygomalic process, which is horizontal and arises by two roots, one anterior covered by cartilage, narrow exter- 442 DUBLIN DISSECTOR. nally, broad internally, runs transversely in front of the glenoid cavity, the other passes horizontally backwards, and bifurcates, one portion turns in to the glenoid fissure, the other is gradually lost above the mastoid process ; where these two roots of the zygoma, the one transverse, the other horizontal, unite, there is a small tubercle to which the ex- ternal lateral ligament of the lower jaw is attached ; the zygoma thence bends forwards and downwards, slightly curved, convex outwards, and ends in a serrated edge which joins and rests on the malar bone ; between the root of this process and the squamous plate there is a smooth trochlea, over which the posterior part of the temporal muscle moves ; behind the transverse root of this process is the articular or glenoid cavity, which is crossed by the Glasserian fissure ; this leads inwards and forwards, into it the capsular Liga- ment is inserted, and near its centre is a small hole through which the corda tympani nerve and the laxator tympani muscle pass; to this fissure also, the processus gracilis of the malleus is attached ; the anterior part only of this ca- vity enters into the maxillary articulation, the posterior is filled by the parotid gland, and is bounded by the auditory process ; this leads inwards and forwards behind the glenoid cavity from the external auditory hole, which is between the two divisions of the outer root of the zygoma; this process or meatus is a twisted plate of bone, united above to the squamous plate, but presenting below a rugged edge to which the cartilage of the ear is attached ; the meatus takes a direction forwards, inwards, and a little downwards, it is narrower about the centre than at the extremities, it leads to the membrana tympani. The squamous plate internally is marked by vessels and by the convolutions of the brain, like the other bones of the cranium; its upper edge is bevelled off and is very rough to overlap the parietal bone. The mamillary or mastoid is the posterior inferior portion, it is joined to the parietal bone above, and to the occipital be- hind, by a very deeply serrated edge, inferiorly it is pro- longed into a rough nipple-like process, the mastoid, internal to which is a groove for the occipital artery, and another partly behind it for the digastric muscle, above and behind it, is a hole [the mastoid foramen] through which a vein and small artery pass; this process is hollowed out into cells which communicate with the tympanum, it gives at- tachment to the sterno-mastoid muscle ; the cerebral sur- face is deeply grooved for the lateral sinus. The petrous portion passes from the junction of the mastoid and squamous forwards and inwards into the base of the skull, it is of a triangular form, the base behind and very irregular, with a deep notch which assists the occipital bone in forming tha DUBLIN DISSECTOR. 443 foramen lacerum posterius ; the apex is anterior^ contiguous to the body of the sphenoid bone, and completing with it the foramen lacerum anterius, which in the recent state is filled up with cartilage ; this bone is peculiarly hard and rugged ; on its inferior surface we remark in front of the foramen lacerum posterius a minute hole which leads to the cochlea, and is named the aqueduct of the cochlea ; more anteriorly and externally is the styloid process which descends obliquely inwards and forwards, and gives attach- ment to three muscles ; it is surrounded at its base or root by a plate of bone most prominent anteriorly and exter- nally, this is named the vaginal process; it separates the glenoid fossa from the carotid foramen ; behind and out- side the styloid process, between it and the mastoid, is the stylo-mastoid hole or the lower end of the aqueduct of Fallo- Eius, this transmits the portio dura or the facial nerve; irt *ont of the styloid process, and a little internal to it-, is the carotid hole which leads into a canal that winds forwards,- upwards, and inwards, and- which opens within the cranium above the foramen lacerunr anterius by the side of the body of the sphenoid bone, it transmits the carotid artery and branches of the sympathetic nerve : in front of the carotid hole is a flat rough surface to which the muscles of the palate are attached. The apex of the petrous bone is very irregular, it lies in the foramen lacerum anterius, the inter- nal opening of the carotid canal is in it ; into the angle be- tween the petrous and squamous portions the spinous part of the sphenoid bone is wedged ; in this angle there are two holes separated by a thin lamina of bone, the upper trans- mits the teasor tympani muscle, the lower is the extremity of the bony part of the Eustachian tube. The superior or cerebral surface presents a prismatic form, a sharp angular ridge to which the tentorium cerebelli is attached, separates its two surfaces, one looks forwards and upwards, the other backwards and inwards ; on the superior we observe ante- riorly a slight depression which corresponds to the Casse- rian ganglion of the fifth pair of nerves; leading from this is a delicate groove which' conducts to a small opening, the hiatus Fallopii. through which the superior branch of the Vidian nerve passes in order to enter the aqueduct of Fallo- pius ; the remainder of this surface is marked by the con- volutions of the brain, and by the eminence of the superior semicircular canal ; on the posterior surface is the mealus auditorius interims, through which pass the two portions of the seventh pair of nerves, it is directed forwards, and out- wards, is lined by dura mater, and is terminated abruptly by a vertical bony process, beneath which is a sort of crib- riform plate, through this the auditory nerves pass, and 444 DUBLIN DISSECTOR. above this the portio dura enters the aqueduct of Fallopius ; the latter is a very long canal, which leads outwards and downwards behind the tympanum ; the hiatus Fallopii and some canals from the tympanum open into it, it ends in the stylo-mastoid foramen ; behind the meatus is a small de- pression lined by the dura mater, and posterior to this is a narrow short slit in which the canal of the vestibule ends, from this slit a groove descends to the jugular opening. The petrous bone contains within it the complicated appa- ratus of the organ of hearing which has been already de- scribed, (page 89.) The temporal bone is connected to five bones, the parietal, malar, sphenoid, occipital, and inferior maxillary, and in some to the os hyoides. In the foetus it consists of two portions, the squamous and petrous, the lat- ter is large and well developed, and the ossicula auditus which it contains are perfect, and nearly as large as in the adult, the mastoid portion is not formed, the styloid process is cartilaginous,, and is distinct from the rest of the bone, the external auditory meatus is wanting, a bony ring sup- plies its place and encircles the tympanum. The processes enumerated are five, viz. the mastoid, auditory, zygomatic, styloid, and vaginal ; the holes are ten proper arid two com- mon ; the proper are, the external auditory, glenoidal, stylo- mastoid, aqueductus cochlea?, carotid, Eustachian, hiatus Fallopii, internal auditory, and aqueductus vestibuli ; the common are the foramen lacerum anticum, and posticum or jugular. [The mastoid foramen may be wholly in the mastoid portion, or wholly in the os occipitis, or common to the two. Muscles. Fourteen muscles are attached to the bone of each side ; eleven arise from it ; the temporal from the squamous plate ; the inasseter from the zygoma ; the occipito-frontalis, digastricus and re- trahens aurem from the mastoid process ; the stylo-hyoideus, stylo- glossus, and stylo-pharyngeus from the styloid process ; the levator palati, tensor tympani and stapedius from the petrous portion : three are inserted into it the splenius capitis^ sterno-mastoid and trachelo- mastoid into the mastoid portion.] The ethmoid bone is situated in the notch between the or- bital plates of the frontal bone, and forms the roof of the nostrils; it is so named from its cribriform or sieve-like appearance, it is of a cuboid figure, and composed of many- thin, brittle, semi-transparent laminae, placed in every di- rection so as to form cells, these enlarge the surface of the nose without increasing the size or weight, for this bone is remarkably light. It consists of a middle perpendicular lamina and two symmetrical portions, its superior or cere- bral surface is broad and covered by the dura mater, in its posterior edge is a notch which receives a process of the DUBLIN DISSECTOR. 445 sphenoid bone, along the middle line is a hard ridge, which anteriorly rises into a remarkable process, the crista galli^ to which the beginning of the falx is attached, this process ends before in two short wings which join the os frontis, and which often assist in bounding the foramen ccecum ; on either side of this process is a channel deeper before than behind, these lodge the olfactory nerves ; anterior to each of these, and nearer to the process, is a small slit [the foramen ovale] which transmits the nasal branch of the ophthalmic nerve ; this entire surface is perforated by numerous holes, about ten or twelve of these are large, and are placed over the lateral parts of the bone, the remainder are very small and are on either side of the median line, they each lead into a small vertical canal lined by dura mater ; from the inferior surface of this plate, there de- scends the nasal lamella in the middle and a large spongy cellular mass on either side ; the nasal lamella is in the me- dian line, it is thick above and behind where it joins the sphenoid, thin below where it joins the vomer and nasal cartilage, and very thick before where it unites to the nasal process of the os frontis and to the nasal bones, its sides are marked with the canals for the olfactory nerves, short and oblique before, vertical and very long in the middle and behind, they descend for about half the depth of the plate, and become converted into mere grooves ; on either side of this septum is a deep channel, which forms the roof of each naris, on each side of this we observe an irregular long structure which consists of three parts, an internal curved lamina, (the superior turbinated bone,) a middle range of cells, and externally towards the orbit a smooth square plate, the os planurn. First, the turbinated or spongy bone is a very thin plate descending at first vertically, and then bending outwards, and rolled upon itself for nearly half a turn ; in the posterior extremity of this is a depres- sion or sort of cleft, which is called the superior meatus of the nose, this channel or meatus extends along the poste- rior half of the ethmoid, it is closed before, except in a small aperture which leads into the posterior ethmoid cells; the portion of the turbinated plate which extends below this fossa is named the middle spongy lone, it is larger than the upper portion, more curved, and very concave out- wardly, beneatb this is a deep fossa named the middle meatus of the nose ; second, the ethmoid cells are external to the turbinated plates, bounded above by the cribriform plate, and externally by the os planum and os unguis, the cells are about twelve or fourteen in number, and are di- vided by a bony septum into an anterior and posterior set, the posterior are small, and open into the superior meatus, 39 446 DUBLIN DISSECTOR. and sometimes one of the uppermost communicates with the sphenoid sinus oropens intothe fossa of its turbinated plate ; the anterior cells are larger and more numerous, they open into the middle meatus, one of the most anterior is curved into a sort of tube, the infundibulum, into this the frontal sinus opens above, and it terminates before the orifice of the great maxillary sinus or antrum ; all these cells are lined by the pituitary membrane, which, however, is less vascular and thick than that on the nasal lamella or turbi- nated bones; on this membrane, particularly that covering the superior spongy bone, and the square surface before it, the external olfactory canals chiefly end ; from the lower surface of the ethmoidal cells thin plates of bone often de- scend very irregularly to join the superior maxillary. Ex- ternal to the cells on each side is the third part, the os pla- num or orbital plate, very smooth and polished, articulated above to the frontal, before to the lachrymal, behind to the sphenoid, and below tb the maxillary and palate bones, the upper border has often a notch or two which assist the frontal in forming' the internal orbital holes. The ethmoid bone contributes to form'the base of the cranium, the nose, and the orbits; it has little or no cellular tissue in its com- position except in the turbinated plates and the crista galli. It is developed by three points of ossification, one for the central lamella and one for each side, the latter appear first, the turbinated plates are not distinct until five years of age : it is joined to two bones of the cranium, the fron- tal and sphenoid, and to eleven of the face, the nasal, su- perior maxillary, lachrymal, palate, interior spongy, and the vomer. [There are no muscles attached to this bone ; its use being to offer in a small space a large surface upon which the impression of odo- riferous particles may be received.] The sphenoid bone is so named from the manner in which it' is wedged into the base of the skull, in the middle of which it is placed, it is articulated to all the bones of the cranium, and to many of those of the face, it' is of a very irregular form, and has been compared to a bat, to which it bears some resemblance, particularly if the ethmoid re- main attached ; it may be divided into a body and proces- ses, the body is in the centre, and resembles a square box; from its median line inferiorly and anteriorly proceeds the azygos process, or the rostrum, which is received between the layers of the vomer, on each side of this is a small groove for vessels ; the body is flat and rough posteriorly for attachment to the basilar process, [of the os-occipitis] its centre is hollowed out into two cavities or sinuses which are separated by a septum, which is continuous with the DUBLIN DISSECTOR. 447 azygos process, anteriorly it presents the two small round openings of the sphenoid sinus, beneath which are often found two small triangular bones, the spongy or turbinated bones of the sphenoid, or of Berlin; the superior or cere- bral surface of the body presents several remarkable ap- pearances, it is hollowed from before backwards into the deep depression called sella-turcica, this lodges the pitui- tary gland, and is perforated by several holes through which small vessels pass to the nose, posteriorly it is bounded by a thin plate which rises perpendicularly, and has a slight knob at each angle named the posterior clinoid process, to each of these the extremity of the convex edge of the falx is attached ; anterior to the sella is the olivary eminence or middle clinoid process, on it is a transverse de- pression for the optic commissure, on each side of which are the anterior clinoid processes, two thick tubercles to which the extremity of the concave edge of the tentorium is at- tached, each of these is perforated by the optic foramen, which is transversely oval and transmits the ophthalmic artery and the optic nerve ; sometimes the anterior is uni- ted to the posterior clinoid process by bone, and somatimes to the olivary process; from each anterior clinoid process there extends forwards and outwards a thin plate of bone, the transverse spine or lesser win^, or wing of Ingrassias, this is united anteriorly to the frontal bone, and forms a part of the orbit, it ends in a point, its posterior edge is thick and rounded, the sphenoidal fold of the dura mater is attached to it, and botlr occupy the fissure of Sylvius on the base of the cerebrum between 'its anterior and middle lobes ; each side of the sella turcica is grooved by the ca- rotid artery ; from its forepart extends a small plate to join the ethmoid bone, (elhmoidal process ;) from each side of the body the ala is continued outwards, forwards, and upwards ; it presents three surfaces, one anterior, smooth and square, forms part of the outer wall of the orbit, and is named or- bital process, another is elongated and concave, and together with the temporal bone supports the middle lobe of the cerebrum ; the third or external surface is named the tem- poral process, this is divided into two by a crest, the upper part forms a portion of the temporal fossa, and the lower of the zygomatic fossa, some fibres of the temporal and external pterygoid muscles are attached to the crest itself; from the posterior part of each wing the spinous process ex- tends backwards, and curves a little downwards and out- wards, and occupies the angle between the squamous and petrous portions of the temporal bone, it terminates in a spine, the styloid process, on the inner side of the articulation of the lower jaw ; near this process is a small foramen 448 DUBLIN DISSECTOR. (spinosum) which transmits the middle or spinous artery of the dura mater, anterior to this is the foramen ovale opening directly downwards for the passage of the inferior maxil- lary nerve; still more anterior is the foramen rotundum, which leads forwards and transmits the superior maxillary nerve ; between the lesser and great wing is a long slit, the foramen lacerum orbitale, wide internally, narrow exter- nally where the frontal bone sometimes assists in closing it, it transmits the third, fourth, first branch of the fifth and the sixth pair of nerves from the cranium to the or- bit : from the angle between the body and ala, the ptery- goid plate descends perpendicularly, internally it bounds the posterior naris, externally the external pterygoid mus- cle is attached to it, anteriorly the palate bone is con- nected to it, posteriorly it is hollowed into the pterygoid fossa, which lodges the internal pterygoid muscle, and in a small depression internal to this the tensor palati muscle; this fossa thus divides this process into two plates, the ex- ternal is broad and rough, tho internal is longer and nar- rower, and ends in the hamular process, a small delicate hook, convex inward?, concave outwards, and covered by a bursa, round this the tendon of the tensor palati muscle turns: in the inferior notch between these plates the palate bone is received ; above the internal pterygoid plate is the Vidian hole or canal, this opens anteriorly on the inner side of the foramen rotundum, into the spheno-maxillary fossa, and posteriorly very small into the foramen lacerum ante- rius. it transmits the Vidian nerve and vessels. The structure of the sphenoid bone is very compact, except the body which is cellular ; the latter about ten years of age undergoes the process of absorption, whereby the cavities called the sphenoid sinuses are formed ; these open into the upper and back part of the nose ; in front of them in the adult is a small curved plate of bone, the sphenoidal turbinated bone, it is of a pyramidal form, the base anteriorly connected to the posterior ethmoid cells, the apex posteriorly, and joined to the forepart of the sinus, it lies above the spheno-palaiine foramen, a hole which is below the body of the sphenoid, and between the orbital processes of the palate bone ; this hole leads from the nose to the spheno- or ptery go -maxillary space ; these su- perior spongy bones are wanting in the child and some- times in the adult. The sphenoid is articulated to the seven bones of the cranium and to five of the face, viz., the two malar, two palate, and the vomer, and in some cases to the superior maxillary by the pterygoid plates, the palate bones however in general intervene ; the pro- cesses enumerated are twenty -seven, viz., five clinoid, ono DUBLIN DISSECTOR. 449 ethmoidal, two lesser wings, one vomer or azygos, two spongy or triangular, two great wings, two temporal, two orbital, two spinous, two styloid, four pterygoid, and two hamular; the foramina are fourteen proper and eight com- mon ; the proper are, two optic, two lacerated orbital, two round, two oval, two spinal, two Vidian, arid the two si- nuses : the common are, two foramina lacera antica basis- cranii, two spheno-maxillary fissures, one in each orbit bounded by the orbital plates of the sphenoid, malar, maxillary, and palate bones, two spheno-palatine, and two posterior palatine canals between the pterygoid processes and the superior maxillary tuberosities. At birth, the sphenoid bone consist of three pieces, one is the body to which the clinoid processes and lesser wings are attached, the lateral pieces consist of the pterygoid processes and the great wing of each side. [Muscles. Twelve pair are attached to this bone ; and all arise from it, the temporal, external and internal pterygoids, constrictor pharyngis superior, tensor palati, laxator tympani, levator palpebroe auperioris, the superior oblique and four recti muscles of the eye.] The bones of the cranium are connected to each other by suture, that is, the edge of each is serrated or cut into irregular teeth like processes, these indigitate or lock into each other, so as to unite the two edges in a very strong and motionless manner, the indentations are irregular nnd oblique in very thick bones, but where the edges are thin, the suture is more straight and regular ; they are more dis- tinct in the young than in the old, and on the outer than the inner surface of the cranium ; there are seven sutures noticed by most anatomists, (some however unnecessarily enumerate a greater number,) the sphenoidal, ethmoidal, coronal, sagittal, lambdoid, and two squamous. The sphe- noidal suture is very extensive, it follows the irregular edge of the sphenoid bone, and connects it to the occipital, the temporal, inferior angle of the parietal, the frontal, and the ethmoid. The ellimoidal suture in like manner encircles the ethmoid bone and connects it to the frontal. The frontal, or coronal suture proceeds .from the upper extremity of the sphenoidal about an inch behind the external angle of the os front is, ascends vertically inclining a little backwards, and then descends to the same point on the opposite side, it connects the frontal and parietal bones in the manner be- fore explained. The sagittal suture leads from the superior angle of the occipital bone directly forwards between the two parietal to the centre of the coronal suture, and is sometimes continued along the median line of the frontal bone down to the nose. The lambdoid suture extends on 38* 450 DUBLIN DISSECTOR. either side from the posterior extremity of the sagittal su- ture, downwards and forwards to the mastoid process of the temporal bone ; a suture named the additame.ntum of the lambdoid continues down between this process and the occi- pital bone as far as the foramen lacerum posterius; the lumbdoid suture is very rough, and frequently contains ossa triquetra of very irregular size, it connects the occipi- tal and the two parietal bones ; the additamentum is very little serrated, but presents uneven thick edges, it connects the occipital to the mastoid portion of the temporal bone, the mastoid hole is frequently in it, it nearly corresponds to the lateral sinus. The squamous suture on each side is continued from the extremity of the sphenoidal in an arched direction upwards and backwards, as far as the inferior angle of the parietal, it is then continued under the name of additamentum of the squamous suture, directly backwards for about an inch ; the structure of the squamous differs from that of the other sutures, the bones are not serrated but thin and scaly, and overlap each other, it unites the temporal to the parietal; the additamentum is serrated and connects the inferior angle of the parietal to the upper part of the mastoid portion of the temporal bone, it corresponds to the course of the lateral sinus internally ; a small os triquetrum is sometimes found at the anterior part of this suture, and seldom in any other situation. [The bones of the cranium belong for the most part to the class of flat bones, and are developed by fibres radiating from a centre. In the adult, the flat bones of the head consist of three laminae, an external table of compact tissue, an internal table of compact tissue, more dense and brittle than the other, and hence called the tabula vitrea, arid a middle lamina of spongy tissue, the diploe ; this does not exist in the infant and child, but subsequently is developed, appa, rently at the expense of the contiguous surfaces of the compact ta- bles, which seem to recede from each other, so as to form the diploe and the frontal sinuses. In the old subject, the diploe is absorbed, and the two compact tables fall together again ; in advanced life the sutures are liable to become obliterated, so that the bones form a solid inseparable mass ; a suture may be confounded with a fissure. All the bones of the cranium may be fractured ; but those parts above a line subtending the supra-orbital arches, the external open- ings of the ears, and the occipital protuberance are of course most exposed to external violence ; those parts in the base of the cranium may be fractured by very great violence, or by a counter fissure. The internal table may be fissured, the external being entire ; and both tables may be driven in without a division of the soft parts over them. There are some situations in which we are directed not to apply the trephine, as over the longitudinal sinus, over the trunk of the middle rneningeal artery, &,c. ; but under certain circumstances we must operate in those places ; the trephine cannot be applied be- DUBLIN DISSECTOR. 451 low the superior transverse ridge of the occipital bone. After a piece of bone has been removed by the trephine, its place is subse- quently supplied by a fibro-cartilacrinous membrane, of which there are some fine specimens in the collection of Dr. Sabine.j OF THE SKULL IN GENERAL. THE outer surface of the skull presents four regions, the superior is smooth and even, has no remarkable appearance deserving more particular attention ; the lateral regions arc each divided into two, anterior or temporal, and the poste- rior or mastoid ; the inferior region extends from the nasal notch to the occipital protuberance, and is bounded late- rally by the zygomatic arches, and by a ridge which is continued from these processes round the skull with but little interruption ; this region may be divided into threo portions, anterior, middle, and posterior ; the anterior ex- tends from the superciliary ridges of the os frontis to the roots of the pterygoid processes of the os-sphenoides ; it presents the nasal spine and process of the os frontis, the ethmoid bone, the orbital plates of the os frontis, bounded by its angular processes before, and by the orbitar plates of the sphenoid behind ; in this division are the supra-or- bital, the anterior and posterior orbital holes, the openings of the frontal and ethmoid cells, the optic and lacerated holes of the orbits, the Vidian canals and the foramina ro- tunda. The middle division extends from the roots of the pterygoid to the styloid processes of the temporal bones, it presents the azygos process, the basilar process of the os occipitis, the anterior points of the petrous portions of the temporal bones ; the spinous processes of the sphenoid, and the glenoid cavities of the temporal bones. The holes in this division are the oval, spinous, carotid, external, au- ditory, glenoidal, and the Eustachian tubes. The posterior division extends from the styloid processes of the temporal to the tuberosity of the occipital bone ; it presents the fo- ramen magnum, the two condyles, the jugular ridge, the styloid processes of the temporal bones, surrounded by their vaginal processes, the mammillary processes, the digastric pits, the inferior and superior transverse arches, the spine, protuberance, and pits of the occipital bono ; the foramina in this division are the stylo-mastoid, mas- toid, magnum, lacera postica, anterior and posterior con- dyloid. The skull is divided internally into the arch or vault and the base ; on the vault is to be observed the sulcus for the longitudinal sinus, the frontal crest, the grooves for the mid- dle arteries of the dura mater, the depressions for the con- volutions of the brain, and for the granulations or glandulse 452 DUBLIN DISSECTOR. Pacchionse ; the base of the skull is very uneven, and pre- sents three portions, regions, or fossae on different planes, the anterior or frontal, the middle or spheno-temporal, and the posterior or occipital ; the first is formed of the orbital plates of the frontal bone, the cribriform plate of the eth moid, and the lesser wings of the sphenoid ; the foramina in this division are the cascum, olfactory, and optic. The second division is bounded before by the transverse spinous processes of the sphenoid, on the sides by the squamous portions of the temporal, and behind by the superior angles of the petrous portions of the same bone, and by the poste- rior clinoid processes of the sphenoid ; in the middle is the sella turcica, on each side of which, but below it, is a groove for the carotid artery, and for the cavernous sinus, and be- low this is a shallow groove tfor the superior maxillary nerve; further out on each side, are the cavities to lodge the middle lobes of the brain ; and on the anterior surface of the petrous bones are seen the juttings of the vertical semicircular canals. The foramina in this .division are, the foramina lacera orbitaria superiora, rotunda, ovalia, caro- tica, spinosa, lacera basis cranii anteriora,. and innominata or hiatus Fallopii. The third or occipital portion is bounded before by the basilar process, and by the posterior surface of the petrous bones, and behind by the occipital, it pre- sents the basilar process, the foramen magnum, the perpen- dicular ridge of the occipital crossed by the transverse, by which this bone is divided into four fossae, the superior an- gles of the petrous bones having a shallow groove for the superior petrosal sinuses, the transverse occipital ridge, with a deep one for the lateral sinuses, which last are continued over the inferior angles of the parietal bones, and thence descend inwards along the mastoid portions of the temporal bone, and then again groove the occipital bone, and pass forwards on it to the posterior foramina lacera ; the per- pendicular ridge is grooved above for the longitudinal sinus, which terminates sometimes in the left, and at other times in the right lateral sinus ; the same ridge below the tento- rium gives attachment to the falx minor, and is slightly grooved for the occipital sinuses. The foramina in thus division are the foramina auditiva, aqueductus vestibulo- rum, foramina lacera postica, foramen magnum, foramina condyloidea antica and postica. THE BONES OF THE FACE. THESE consist of six pair and two single bones ; the six pair are the malar, superior maxillary, lachrymal, nasal, palatine, and inferior spongy ; the two single bones are the vomer and the inferior maxillary. DUBLIN DISSECTOR. 453 The malar or cheek bone is placed at the outer and under part of the orbit, and forms the prominence of the cheek ; it is of an irregular square form, convex externally, and covered by the skin and orbicularis palpebrarum ; it pre- sents one or two small holes for vessels and nerves; its upper and outer edge is named, [superior or~\external obital procsss, and joins the frontal bone ; its inner end is cut off obliquely and serrated, is attached to and overlaps the maxillary bone, this is the maxillary process; its anterior edge between these two processes is round, smooth, and concave, forms about one-third of the base or circumference of the orbit, and ends internally in a long angle, named the inferior orbital process ; the lower edge is thick and uneven, and gives attachment to the masseter muscle, it ends poste- riorly in the zygomatic process, which passes backwards, and terminates in a serrated edge which supports the zygomatic process of the temporal bone; behind this the malar bone is smooth, and forms part of the temporal fossa ; from the posterior surface a thin plate extends into the orbit, and is named the internal orbital process ; the posterior edge of this is notched to close the spheno-maxillary fissure anteriorly. The malar bone is thick, strong, and cellular ; it is well developed in the foetus. It is joined to four bones, the frontal, sphenoid, temporal, and superior maxillary ; the processes are five, the superior, inferior, and internal orbi- tal, the malar, and zygomatic ; the foramina are two or three proper and one common, viz., the spheno-maxillary fissure, or the foramen lacerum orbitale inferius. [Muscles. Four muscles arise from this bone, the zygomatici ma- jor and minor, the masseter, and the temporal ; the orbicularis pal. pebrarum spreads over it.] The superior maxillary Imne is of a very irregular figure, and attached to all the bones of the upper jaw ; it forms part of the front of the face, a portion of the orbit, nose, and palate ; it may be divided into the body and processes. The body is concave anteriorly, to form the infra-orbital or canine fossa, in the upper part of which is the infra-orbital hole ; it is bounded externally and above by a rough ser- rated surface, the malar process, which is smooth and hol- lowed out behind for the temporal muscle ; springing from the inner and upper part of the body, is the nasal process of a pyramidal form, perforated by one or two small holes for vessels, serrated above to join the os frontis, prominent below, slightly grooved anteriorly to receive the nasal bone and the alar cartilage, and deeply grooved behind to form part of the lachrymal fossa and duct: its internal surface forms part of the nasal fossa, and is connected to the eth- moid bone above, below this is a channel that leads to the 454 DUBLIN DISSECTOR. middle meatus, and inferior to this is a crest for the spongy bone ; between the nasal and malar processes is the orbital plate, of a triangular form, the base joined to the ethmoid, lachrymal, and palate bones; this process looks down- wards and forwards; its outer and posterior edge bounds the spheno-maxillary fissure : the infra-orbital canal, which runs along it in a direction forwards and inwards, lodges the vessels and nerves of that name ; this canal divides anteriorly into two, the smaller is the anterior dental, which descends in the anterior wall of the antrum, where it teiv minates by communicating with the anterior alveoli, the other or the proper infra-orhifal canal is wider, and ends in the infra-orbital hole ; the edge of the bone above this hole is round to form part of the contour of the orbit, behind which the inferior oblique muscle of the eye arises ; behind and below this plate is the tuberosity, this is more prominent in the young, as it contains the last molar tooth, after the protrusion of which it diminishes, near this are three or lour small holes, the posterior dental canals, which lead to the posterior alveoli ; beneath the orbital plate, the body of the bone is excavated into a large cavity, the antrum highmorianum, [or maxillary sinus,] of somewhat a trian- gular figure, the base towards the nose, the apex towards the malar process ; this is the largest sinus connected with the nose, it is sometimes divided by septa as well as by the anterior dental canal into two or more cells ; the infra- orbital canal runs along its roof, through the floor, one or two of the molar alveoli project and sometimes open, the canine fossa is in front of it, and the'tuber bounds it behind, this cavity is lined by the membrane of the nose ; in the skeleton the opening in its base is very large and irregular, but in the natural state it is contracted by the ethmoid bone above, by the palate bone behind, and by the inferior spongy bone below, also by the lining membrane of the nose ; it opens by one or two small oblique openings into the middle meatus of the nose, anterior to which is the in- fundibulum, a deep groove leading downwards, backwards, and inwards, from the frontal sinus and the anterior eth- moid cells, and opening into the middle meatus; the body of this bone is bounded below by a strong horizontal plate, the palatine process, the upper surface of which is smooth and concave, and forms the floor of the nose, the lower is rough, and forms the roof of the mouth ; it is thick before, thin and serrated behind to join the palate bone, internally it is thick and rough, and joins the opposite bone, by a su- ture, in the anterior part of which is the anterior palatine canal, which opens inferiorly on the palate by the foramen incisivum, and superiorly by two distinct holes, one in each DUBLIN DISSECTOR. 455 nostril ; this internal edge is raised so as to form the nasal spine or crest to receive the vomer, anteriorly this projects so as to form the anterior nasal spine, to which the cartila- ginous septum of the nose is attached; between this and the nasal process the bone is very concave and forms the anterior opening of the nares. The palate plate is bounded anteriorly and externally by the curved alveolar edge or process; this is very thick, particularly behind, and is divided into several, generally eight, conical cavities for the teeth ; the partitions between these are formed of dense cellular texture which is less compact posteriorly. The superior maxillary bone is con- nected to two bones of the cranium, the frontal and eth- moid, and to seven bones of the face, the nasal, lachrymal, malar, palate, inferior spongy, vomer, and to its fellow of the opposite side, also to the teeth ; it is sometimes con- nected to the pterygoid processes of the sphenoid. The processes are eight, the nasal r orbital, malar, tuberosity, alveolar, palatine, nasal crest,- and nasal spine : the fora- mina are three proper and four common ; the proper are the infra-orbital, the foramen antri, and foramen incisivum ; the common are the spheno-maxillary fissure, the posterior palatine hole or canal, the anterior nares, and the nasal or lachrymal duct ; this bone is well developed in the foetus,. with the exception of the alveoli and sinus, the former com- mence about the end of the first year, the latter about the seventh. [Muscles. Eight are attached to this bone ; seven arise from it; the obliquus oculi inferior, levator and depressor labii superioris alseque nasi, levator anguli oris, compressor nasi, buccinator and masseter ; the orbicularis palpebrarum Is inserted into it.] The palate bone is situated' at' the outer and back part of the nose,. bet, ween the pterygoid processes [of the sphenoid], and the superior maxillary bone, it is of a very irregular figure and may be divided imo four parts; first, the hori- zontal or palate plate; second, the nasal or perpendicular plate, at the lower and outer angle of which is, third, the pterygoid process;, and fourth, at the upper extremity of the nasal is the orbital portion.- The palate process or plate is nearly square, flat, and rough below, smooth above, and concave from side to side to form part of the floor of the nose, posteriorly it has a thin edge to which the velum palati is attached ; its anterior border is serrated to join the palate plate of the maxillary bone, its inner edge rises into a spine or crest to support the vomer, and is continued posteriorly into the posterior nasal spine; its centre is thinner than its edges. The nasal process or vertical plate is broad and thin, rests partly on the maxillary bone, its inner or 456 DUBLIN DISSECTOR. nasal surface forms part of the nasal fossa, and is marked by two depressions which assist in forming the lower and middle meatus of the nose, the ridge between these sup- ports the lower spongy bone, externally it is uneven and grooved for the posterior palatine vessels and nerves : the anterior edge of this plate is thin and brittle, and prolonged for some way over the antrum, the posterior edge joins the pteryguid processes [of the sphenoid.] The luberosity or the pterygoid process arises from the lower and outer angle, is thick and wedge-shaped, it inclines backwards and out- wards, and presents three fossae, one at each side for each pterygoid plate [of the sphenoid,] and one in the middle which assists in forming the pterygoid fossa ; the inner- most of these fossa? is the deepest : this process is perfo- rated by one or two small holes which lead from the pala- tine canal ; at the upper extremity of the nasal plate arc the orbital and sphenoidal processes, separated from each other by a deep notch : the orbital is the larger and ante- rior of the two, it is triangular and bent a little outwards, it appears in the most remote part of the floor of the orbit, where it is joined to the maxillary bone by one edge, to the os planum by the second, while the third enters into the spheno-maxiilary fissure ; the sphenoidal or posterior or- bital process is smaller, and is articulated to the body and spongy plate of the sphenoid bone ; both these processes are cellular, the cells communicate with those of the eth- moid and sphenoid bones; the notch between these two processes forms the spheno-palatine hole. The palate bone is joined to the maxillary, inferior spongy, vomer, sphenoid and ethmoid, and to the opposite palate bone ; it is composed of thin compact substance, and is well formed in the foetus ; its processes are seven, palate, nasal, ptery- goid, orbital, sphenoidal, posterior nasal spine and crest ; its foramina are one proper and three common. The pro- per is the posterior palatine hole or holes ; the common are the posterior palatine or ptery go-maxillary canal, the spheno-maxillary fissure, or the foramen-lacerum orbitale inferius, and the spheno-palatine hole; the latter is above the nasal plate, below the body of the sphenoid, and be- tween the orbital processes of the palate bone, it transmits the nasal nerve and artery from the spheno-maxillary fossa into the nose. [Muscles. With the exception of the azygos or motor uvulae no muscle arises to any extent from this bone ; the tensor palati and pterygoid muscles are slightly attached to it.] The inferior spongy or turbinated bone, placed on the lower part of the outer side of the nose, elongated from before DUBLIN DISSECTOR. 457 backwards, presents a wrinkled or a rugged surface, is convex towards the nose, concave outwards, its lower edge is loose, spongy, and curled outwards ; the upper edge is uneven, thin, and joined to the unguis, and to the maxil- lary and palate bones ; it is connected to the unguis by a thin pyramidal process, which completes the nasal duct ; it is also in general united to a descending oblique process of the ethmoid, it is composed of very thin brittle sub- stance; marked with pores and little spines. [No muscles are attached to this bone, or to the vomer, these and the ethmoid being the only bones of the head and face which have no muscular relations.] The os unguis or lachrymal bone is placed at the inner and orepart of the orbit ; below the os frontis, behind the lasal process of the superior maxillary and before the. thmoid bone, it is of an oblong square shape, and very hin, it covers the anterior ethmoidal cells ; externally it is ivided by a perpendicular ridge, which terminates below n a little hook-like process, into two unequal plates, the losterior or orbital plate is short and broad, the anterior achrymal plate is concave, long, and narrow, and forms part )f the lachrymal or nasal fossa and duct. The os unguis s joined above to the internal angular and orbitar pro- :esses of the os frontis ; behind to the os planum of the 'thmoid, below to the orbitar plate of the maxillary, before o the nasal process of the same, and before and below to he inferior spongy bone; its structure is thin but com- Dact. [This bone is sometimes wanting, and its place is then supplied iy the superior maxillary and ethmoid bones : this bone co-exists with the lachrymal secretion, and is said not to be found in those ani- mals, who, living in water, have no lachrymal gland. The tensor arsi arises from this bone.] The nasal bones are situated beneath the nasal process of he frontal and between the nasal processes of the superior maxillary bones, they are small, narrow, and thick above, hin and expanded below ; they form the bridge of the nose ; the external surface of each is slightly concave from above downwards, convex from side to side, and perforated with one or two small holes ; the internal surface is con- cave and grooved for the nasal nerves ; the superior mar- jin is thick and deeply denticulated to join the nasal process and spine of the frontal and the nasal plate of the ethmoid bones ; its external edge is grooved and received into the nasal process of the superior maxillary, its inner edge is flat to join with its fellow, and its lower edge is thin and irregular, joins the alar cartilages, and is notched for 39 458 DUBLIN DISSECTOR. the passage of the nasal branches of the ophthalmic nerve. [Muscles. No muscles are attached to this bone, but the pyrami- dalis and compressor nasi are inserted into the integuments over it.] The vomer ; this azygos bone resembles a ploughshare; it stands in the median line, although it often bends a little to one side, is thin and flat, and covered by the pituitary membrane, it presents four edges ; the upper or sphenoidal is hollowed to receive the azygos process ; the anterior is slightly grooved to receive the ethmoidal lamina and the nasal cartilage ; the posterior or pharyngeal is round and smooth and unattached ; the inferior or palatine edge is the longest, and is received between the laminae of the nasal crest of the maxillary and palate bones ; it is attached to the maxillary, palate, ethmoid, and sphenoid bones, also to the turbinated bones of the latter ; its structure is compact, but thin and transparent : all the bones of the upper jaw are well developed in the foetus. [The bones of the upper jaw generally will only be fractured by very severe violence ; but the nasal bones are most exposed and most frequently broken ^congenital deficiencies are occasionally met with, as in cleft palate, in which parts of the superior maxillary and palate bones are wanting, and the vomer is either wanting, or bent to one side. In acephalous monsters the bones of the face may be perfect, but there is great deformity and deficiency in the cranial bones. Large masses of the upper jaw extending even to the sinus and orbit have been successfully removed on account of malignant disease.] The inferior maxillary bone, or the lower jaw, is the largest of the facial bones, it is of a semicircular figure situated at the lower part of the face and extending along its sides and back part to the base of the skull ; it is divided into the body or chin, the sides, the rami, and the processes. The body is the anterior prominent portion with a vertical ridge in the centre, the symphysis, or the line of union of the two symmetrical pieces of which this bone in infancy con- sisted ; inferiorly the body projects into the mental process or chin, above this on each side is a depression for the mus- cles of the lower lip, external to which and looking back- wards is the oval oblique opening of the dental canal, call- ed the mental hole, through which a vessel and nerve of the same name pass ; posteriorly the body of the bone is con- cave, and lined above by the mucous membrane, in the middle it presents, in the line of the symphysis, a chain of eminences, to the superior of which the frasnum lingua adheres, to the middle the genio-hyo-glossi, and to the in- ferior the genio-hyoidsei muscles ; above and on each side Of these are depressions for the sublingual glands, and at- DUBLIN DISSECTOR. 459 the lower border are two depressions for the digastric mus- cles. The sides of the maxilla have a direction backwards and outwards, on their outer surface is an oblique line which passes backwards and upwards to the anterior edge of the coronoid process, it gives attachment before to the platys- ma and depressor anguli oris, and behind to the buccinator muscles ; internally also is an oblique line, parallel to, but more prominent than the external, to this is attached the mylo-hyoid muscle anteriorly, and the superior constrictor of the pharynx posteriorly ; beneath this line is a slight groove which contains the mylo-hyoid nerve, and below this an oblong depression for the submaxillary gland ; the lower edge or base of the jaw is rounded, thick before, thin behind, and grooved opposite the second molar tooth for the facial artery ; the upper or alveolar edge is broad pos- teriorly and bent a little inwards ; it has usually sixteen alveoli, which, as in the upper jaw, vary in form according to that of the teeth. The angle of the jaw is more or less obtuse, and often bent a little outwards; the masseter ad- heres to it externally, the internal pterygoid internally, and ther stylo-maxillary ligament to the border of it. The ra- mus ascends a little backwards, is thick and round posteri- orly, and is enveloped by the parotid gland, externally it is covered by the masseter, internally it presents a deep groove which leads to a large hole, the inferior dental or maxillary; this is situated near the centre of the ramus, and is pro- tected internally by a prominent spine into which the in- ternal lateral ligament is inserted, a slight groove leads from this hole to the mylo-hyoid muscle ; the dental hole leads into a canal which traverses the side of the bone beneath the alveoli, with each of which it communicates ; it con- tains the dental nerve and vessels ; below the incisors this canal turns back a little, and ends at the mental hole ; .his canal is nearer the inner surface of the jaw behind, arid the outer surface before ; the ramus ends above in a notch and two processes, the anterior or coronoid, the posterior Or condyloid ; the notch is traversed by the masseter nerve and vessels. The coronoid -process is triangular, the apex is inclined a little outwards, it is embraced by the insertion of the temporal muscle. The condyle is an oblong convex process supported by a neck which is most depressed an- teriorly, for the insertion of the external pterygoid muscle ; the condyle is curved forwards and most convex in that di- rection ; it is directed obliquely backwards and inwards, so that its internal extremity is posterior, it is also higher than the external ; its posterior surface is nearly straight, and almost free from cartilage. By these processes the lower maxilla is articulated with the temporal bones ; on 460 DUBLIN DISSECTOR. the external edge of each is a tubercle for the insertion of the external lateral ligament. The lower jaw in the young subject always consists of two symmetrical pieces, each angle is very obtuse, and the condyles are directed more upwards than in the adult. [In many of the inferior animals this bone consists of two pieces during life ; and in serpents there is motion at the symphysis ; the angle is obtuse in children, nearly right in the adult, and obtuse again in old age : fractures of this bone may occur in the body or rami ; and portions of it have been successfully removed for osteo sarcoma. Muscles. Fourteen pair are attached to this bone ; eight pair arise from it ; the levator and depressor labii inferioris, depressor anguli oris and buccinator from its anterior surface ; the mylo-hyoideus and constrictor pharyngis superior from the mylo-hyoid ridge ; and the genio-hyo-glossus and genio-hyoideus from the posterior surface of the symphysis. Six pair are inserted into it ; the rnasseter at the junc- tion of the body and ramus ; a few fibres of the platysma myoides ; the digastric into the digastric fossa ; the temporal into the coronoid process; and the pterygoidei internus and externus into the internal surface of the ramus and neck.] The teeth are small, hard bones, thirty-two in number in the adult, sixteen in each jaw ; their form is generally co- nical, the apex in the aveoli ; in each tooth we distinguish the crown, neck, and root ; the crown is external to the al- veolus, it has no periosteum, but is covered by a firm, white, vitreous substance, named enamel : the neck is surrounded by the gum, and the root is firmly held in the alveolus by a mode of connexion called gomphosis. The teeth are di- vided into three classes, the incisores, the canini and the molares : the incisores are four in each jaw, the crown of these is sharp and wedge-shaped, convex before, and thick- ly covered with enamel; those in the upper are stronger than those in the lower jaw ; the former are broader, their edge is like a chisel, cut off posteriorly, the latter are more vertical, their anterior surface is bevelled off, but they are not so sharp as those in the upper jaw, their roots are larg- er ; the canine teeth or cuspidati are two in each jaw, the crown is conical, a little blunt, convex before, their root is single but very long ; the grinders or molares are ten in each jaw, the crown of these is broad and irregular, the roots 'are rfiore or less divided ; the upper grinders are stronger than the lower, the axis of the former is directed outwards, in the latter it is vertical ; the two first molar are called bicuspidati, and are smaller than the canine ; they have only two tubercles on the crown and the fang is single, but some- times it is double ; the posterior grinders are the true molar or multieuspidati, these are large, the crown has four or five DUBLIN DISSECTOR. 461 tubercles, the root has three or four divisions, and each is perforated by a small hole. The teeth are composed of a very compact bone or ivory, less brittle than the enamel ; the latter only covers the crown as far as the neck ; the ivory has no cells in it, its fracture is silky : in addition to the component parts of bone it also contains some fluate of lime ; it possesses the power of resisting the action of the air a long time ; the enamel is very white, and so hard as to strike tire with steel ; it is composed of fibres which are perpendicular to the surface of the crown, it is thicker where the teeth are exposed to much friction, it does not contain any vessels or nerves, and is not regenerated when once destroyed ; each root is perforated with a small hole which leads into the cavity in the crown ; this cavity con- tains a pulp which is very vascular and nervous. [In the infant the germs of fifty-two teeth exist ; of these twenty make their appearance during the period of lactation, and hence they are called the milk teeth ; they are also called nonpermanent or deci- duous ; they are divided, according to form and function, into inci- sores, four in each jaw, cuspidati, two in each jaw, and molares, four in each jaw ; generally these teeth begin to appear about the sixth month, and are complete from the twenty-fourth to the thirtieth month ; at about six years they begin to give way to the permanent teeth, which are usually all complete about the twelfth year, except the two last molar of each jaw, the denies sapientite, which make their appearance from the eighteenth to the twentieth year. The time at which the different teeth appear, however, varies much in different subjects ; sometimes children are born with teeth, and some- times a third set appears in extreme old age. Supernumerary teeth are not very rare, generally but one or two in number, occasionally more ; in the collection of Dr. J. K. Rodgers, there is an inferior maxilla, which had twenty or twenty-two teeth. Caries is the most common disease of the teeth ; the tartar which accumulates round the teeth is looked upon as a secretion from the gums.] The bones of the face are connected by sutures in the same manner as those of the cranium, it is unnecessary to describe these individually, as they are all named from the particular bones they unite. The facial bones, in addition to forming the general outline of the face, also bound seve- ral regions, namely, the nose, orbits, and the palate, also the temporal, zygomatic, and spheno or pterygo-maxillary fossse. The bones entering into the nose, have been already mentioned in the description of the organs of sense : on the other regions we shall make a few remarks. The orbits are of a pyramidal figure, the base looking out- wards and forwards, the apex backwards and inwards: seven bones enter into the parietes of each, the frontal, sphenoid, ethmoid, lachrymal, maxillary, palate, and malar ; the upper wall or the roof of each orbit is formed by the 39* 462 DUBLIN DISSECTOR. frontal and the lesser wing of the sphenoid, it is concave, and presents the optic hole posteriorly and the depressions for the lachrymal gland and for the trochlea anteriorly ; the floor is nearly plane and looks outwards and down- wards, it is formed of the malar, maxillary, and palate bones, the infra-orbital canal extends along it : the exter- nal wall is formed by the sphenoid and malar bones, and the internal, which is smooth and plane, is formed by the lachrymal, ethmoid, and sphenoid bones. The bones which form the base of the orbit are the frontal, malar and max- illary ; the foramina in the base of the orbit are four, viz. the supra-orbital, the infra-orbital, the malar, and the nasal duct ; within the orbit are five, viz. the optic, which is in the upper, inner and posterior part, the foramen lacerum superius which leads from the apex upwards and outwards, the internal orbital holes which are found in or close to the suture along the internal wall, and the spheno-maxillary fissure or the inferior lacerated hole which leads from the back of the orbit forwards and outwards along the floor, this slit-like opening is bounded by the sphenoid, palate, maxillary and malar bones. The axes of the two orbits are oblique lines, which, if produced posteriorly, would de- cussate about the sella turcica, while anteriorly they would diverge. The palatine region is composed of the palate plates of the superior maxillary and of the palate bones, and is bounded by the alveolar arch, by the pterygoid processes of the palate bones and by the hamular processes of the sphenoid; to its posterior edge the soft palate and uvula are attached ; anteriorly it presents the foramen incisivum or the anterior palatine canal, and posteriorly the orifices of the two posterior palatine canals. The temporal fossa is placed on the side of the cranium and face ; it is bounded internally by the frontal, sphenoid, parietal and temporal bones ; its extent superiorly is defined by the semilunar ridge on the side of the cranium, which is marked on the frontal and parietal bones, anteriorly by the malar bone, posteriorly by the pulley-like root of the zygomatic process, and inferiorly and externally by the zygomatic arch which is formed by the processes of that name from the temporal and malar bones ; this a -ch is concave above and internally, convex below and externally. The zygomatic fossa is continuous with the lower part of the last described region, from which it is distinguished by a transverse ridge or crest upon the root of the great wing of the sphenoid bone, from this it extends to the tuberosity of the maxillary bone, and is bounded externally by the ramus of the lower jaw. DUBLIN DISSECTOR. 463 The pterygo-maxillary fossa is a very narrow space, is en- closed between the pterygoid processes behind, the tuber- osity of the maxillary bone before, and bounded internally by the nasal lamella of the palate bone, which separates it from the nose ; it contains the spheno-palatine ganglion and the internal maxillary artery. It is immediately below and behind the orbit, with which it communicates by the spheno-maxillary fissure, it also communicates with the palate by the posterior palatine canals, with the nose by the spheno-palatine hole, with the face by the infra-orbital canal, and it also opens directly into the temporal and zygomatic fossae ; the branches of the second division of the fifth pair of nerves pass off through these several com- munications. THE BONES OF THE EXTREMITIES. The extremities are two superior, and two inferior. The inferior extremity is divided into three parts, the thigh, leg, and foot ; the latter is subdivided into the tarsus, meta- tarsus, and toes : the thigh has one bone, the femur ; the leg three, the patella, tibia, and fibula ; the tarsus seven, the astragalus, calcaneum, cuboid, scaphoid, and three cuneiform ; the metatarsus five, and the toes fourteen : thirty bones in all, [exclusive of the two sesamoid bones of the great toe.] The femur is the longest bone in the system, it consists of the body or shaft and two extremities ; the body is slightly twisted, thick above, very broad below, contracted and nearly cylindrical in the centre, arched and smooth before and concave behind, with a sharp, rough ridge down the centre, named the linea aspera, this extends along the middle third of the bone, parallel to its axis, and divides above and below into two ridges, these pass superiorly one to each trochanter, that to the inner being the shorter ; and inferiorly one to either condyle ; these inferior divisions separate further, and enclose a flat triangular space, the popliteal ; this line is very prominent about the centre, and presents two lips and an interstice, for the attachment of different muscles : the anterior convex surface of the fe- mur is broader towards either end than in the centre, it is a little concave superiorly, the sides are slightly flattened, and the external is somewhat narrower than the internal, particularly above ; above the middle of the linea aspera one or two holes may be seen to enter obliquely upwards, these transmit the nutritious or the medullary vessels of the bone ; to the linea aspera in the middle of the thigh, the vastus externus, the adductor tendons, and the vastus inter- nus, are attached ; to its superior external branch which 464 DUBLIN DISSECTOR. leads to the great trochanter and is very long, the adductor rnagnus, glutceus maximus, and vastus externus are attached ; the internal branch is short and not very distinct, it leads to the lesser trochanter, and gives attachment to the adduc- tor brevis, pectinseus, vastus internus, and some fibres of the iliacus internus ; to the lower and external branch of the linea aspera, the vastus externus and short head of the biceps are attached, and to the lower and internal, the vas- tus internus and adductor magnus adhere ; these lines con- tinue as low as the condyles, the internal is smooth and nearly obliterated near its middle for the passage of the crural artery. The upper or pelvic extremity of the femur presents three eminences, the head for articulation with the coty- loid cavity, and the trochanters for the insertion of muscles. The head is of a globular figure, and forms a considerable segment of a sphere, it is directed upwards, forwards, and inwards; a little below its centre, there is a rough depres- sion for the insertion of the -round or articular ligament; with the exception of this depression the head is covered throughout with cartilage ; it is supported by an elongated process, the neck, which forms an angle, more or less obtuse, with the shaft of the bone, the direction of this process is upwards, inwards, and a little forwards, it is flattened before and behind, thicker at the shaft than at the head, its lower edge is longer but smaller than the upper ; a rough irregu- lar line separates the head from the neck, beyond which the articular cartilage does not extend, and at its juncture to the shaft two rough [intertrochanteric] lines extend in- wards and downwards, from the great to the lesser trochan- ter, one on the fore, the other on the back part of the bone, into these the capsular ligament is inserted. The great trochanter is continuous with the external side of the shaft, and nearly in a line with its axis, it is on a little lower level than the head, it is thick, rough and square, externally it is broad and convex, the tendon of the glutseus maximus moves over this surface and an intervening bursa, a prominent ridge bounds it below, to this some fibres of the vastus externus are attached, internally it presents a pit or digital cavity which receives the tendons of the external rotators of the limb, namely, the pyriform, gemelli, and obturators ; the summit of the trochanter is thick and rough, the glutseus medius is inserted into it, the anterior edge is broad, and gives attach- ment to the glutseus minimus, into the posterior, which is round and thick the quadratus femoris is inserted. The lesser trochanter is a conical projection at the posterior and inner side of the shaft, and is considerably below the great trochanter ; it looks backwards and inwards, the tendons DUBLIN DISSECTOR. 465 of the psoas and iliac muscles are inserted into it behind its apex, a bursa is connected to it anteriorly. The inferior or tibial end of the femur is very large and broad, and divi- ded into two eminences or condyks which are separated posteriorly by a deep [intercondyliac] notch ; the condyks articulate with the tibia ; the external is larger, and projects more forward than the internal, its articulating surface is also broader and ascends higher, externally it is rough and presents a tuberosity which gives attachment to the exter- nal lateral ligament of the knee joint ; this is less promi- nent than the internal tubercle ; beneath this tubercle is a groove which receives the tendon of the poplitseus muscle in the flexed position of the joint : internally this condyle presents a rough surface, towards the posterior part of which the anterior crucial ligament is inserted, it is very convex behind, flat before, and broad below. The internal condyle is narrower, less prominent before but prolonged more behind ; it is also longer than the external, and therefore descends lower when the femur is vertical, but both are nearly on a level when the bone is in its ordinary oblique direction ; on its inner side is the tubercle for the attach- ment of the internal lateral ligament of the knee and for the adductor tendon ; to its outer side, which is rough, the posterior crucial ligament adheres ; both condyles are more convex behind than before, they are separated poste- riorly by a deep uneven notch, which lodges the crucial ligaments and is deprived of articular cartilage ; anteriorly they are continued into each other, and unite in a pulley- like surface which is convex from above downwards, and concave from side to side, higher externally than internal- ly ; this trochlea is chiefly formed on the external condyle, it supports the patella: the femur is articulated superiorly with the ilium, inferiorly with the tibia, and anteriorly with the patella; like all long bones it is composed of compact tissue in the centre and cellular at the extremities, the com- pact has a fibrous appearance, the whole shaft is tra- versed by a distinct medullary canal, which is crossed by numerous bony Iamina3 ; the femur is developed by five points of ossification, one for the shaft, one for the tibial end, one for the head, and one in each tronchanter. [This bone is the seat of various fractures; as fracture of the neck within the capsular ligament, fracturing off of the trochanter major, fracture below the trochanters, fracture at almost any point of the shaft, and fracturing off of one or the other condyle. It is also the seat of several diseases affecting either the compact tissue of the shaft, or the spongy tissue of the extremities. Muscles. Twenty. two muscles are attached to this bone on each side ; seven arise from it : the vasti externus and internus, and cm- 466 DUBLIN DISSECTOR. reus from its surfaces and linea aspera ; the short head of the biceps flexor cruris from the external lip of the linea aspera below its mid. die ; the gastrocnemius from both condyles posteriorly ; and the pop. liteus and plantaris from the external condyle : fifteen are inserted into it; the glutei medius and minimus into the trochanter major ; the pyriformis, two gemelli, and two obturatores into the digital fossa ; the quadratus femoris into the posterior intertrochanteric line ; the psoas magnus and iliacus internus into the trochanter minor; the pectineus and three adductors into the linea aspera by its internal lip; and the glutens maximus into the superior half of its external lip.] The bones of the leg are the patella, tibia and fibula. The patella or rotula or knee cap is a small bone in front of the knee joint, of a triangular figure, the base above, the apex below, its anterior surface is convex and covered by skin, a bursa, and some tendinous fibres, it is mark- ed by several longitudinal lines, and presents a very fibrous appearance ; the posterior surface is covered with cartilage and divided by a prominent vertical line into two lateral portions, of these the external is larger and deeper than the internal ; beneath these is a small triangular depressed surface into which the ligament of this bone is insert- ed ; the upper edge is round and cut oft' obliquely back- wards and downwards, to it the extensor tendons are attached ; the patella is of a cellular structure, and cover- ed by a compact lamina which is very dense, and tra- versed by longitudinal strice ; it is developed from a single point of ossification, and remains for a long time cartilagi- nous ; .it is articulated with the condyles of the femur, and connected to the tibia by a powerful ligament ; it protects the forepart of the knee, and serves as a medium of con- nexion between the extensor tendons and the leg. [This bone is the scat of three fractures, the longitudinal, trans- verse, and stellated. Four muscles are inserted into this bone, the two vasti, the rectus femoris and crureus.J The tibia, next to the femur, is the longest bone in the skeleton, it occupies the anterior and inner part of the leg, its upper extremity is thick and expanded from side to side, its circumference Is somewhat circular or oval, convex on the front and sides, but slightly grooved behind ; on either side is a protuberance, that on the internal is the more pro- minent for the insertion of the internal lateral ligament and the tendon of the serni-membranosus muscle ; a little behind the external tuberosity is a small rounded surface looking downwards, covered with cartilage for articulation with the head of the fibula ; on the anterior part of the head is a convex triangular surface looking forwards and downwards, pierced with many vascular holes, and termi- DUBLIN DISSECTOR. 467 nating in a tubercle, to the upper part of which a bursa adheres, and into the lower the ligamentum patellae is in- serted. The upper or femoral surface of the tibia presents two concave or articulating surfaces or condyles covered with cartilage, for articulating with the femur, the internal is oval and the deeper of the two, it is also larger from be- fore backwards ; the external is nearly circular, very super- ficial, and looks obliquely downwards and outwards ; these are separated by a spine, which is of a pyramidal form, inclines upwards and inwards, and is surmounted by two tubercles ; it is nearer the back than the forepart of the bone ; a large, flat, depressed surface lies anterior to it, and a smaller depression behind it ; the semilunar cartilages and the crucial ligaments are inserted into these ; the body of the tibia is triangular, its size diminishes from its head for about two-thirds down, it then increases somewhat towards its lower end ; its inner side is convex above and a little concave below, it is directed obliquely forwards, is covered superiorly by the tendinous expansions of the sar- torius, gracilis, and semitendinosus, but the remainder of it is subcutaneous ; the external side appears a little twisted, it is concave above to support the tibialis anticus muscle, but convex below to support the tendon of that muscle, as also those of the extensors ; its posterior surface, which is also broader above than below, is slightly convex ; it pre- sents superiorly a prominent line passing obliquely down- wards and outwards for the insertion of the popliteeus and the origin of the solreus and the deep flexors ; near this line is the opening of the large canal that leads the vessels to the medullary membrane, it slants obliquely downwards and forwards. The tibia presents three edges, one is ante- rior and commences from the tuberosity, it is very promi nent about the middle, but less so above and rounded below, this line is subcutaneous, it is twisted like the tibia itself, and is commonly called the crest or the shin, the inner edge is thick and round, and more distinct below than above, the outer edge is thin, and gives attachment to the interos- seous ligament ; it is less distinct and bifurcated below. The lower or tarsal end of the tibia is somewhat square, presents an anterior convex edge covered by the extensor tendons, a posterior nearly smooth edge traversed by a groove for the tendon of the flexor pollicis longus ; exter- nally is a concave triangular surface, rough above for liga- ments, and smooth and cartilaginous below to receive the lower end of the fibula ; internally the tibia ends in a thick, flattened, perpendicular process, the internal malleolus or ankle ; it is convex and subcutaneous, it lies anterior to the superior internal tuberosity or condyle, on account of the 468 DUBLIN DISSECTOR. twisting of the bone ; the outer side of this process is smooth and cartilaginous, and joined at right angles to the cavity at the lower end of the bone; it is articulated to the side of the astragalus, its anterior edge is convex and gives attachment to ligaments, its posterior edge is grooved su- perficially for the tendons of the tibialis posticus and flexor communis; the extremity of this process is broad and descends lower before than behind, it gives origin to the internal lateral ligament of the ankle ; the lower surface of the tibia is quadrilateral, concave from before back- wards, and somewhat convex from side to side, being tra- versed from before backwards by a very superficial ridge or prominence, this surface is broader externally, it is bounded internally by the internal malleolus, and exter- nally by the fibula ; the tibia is articulated to the femur, the fibula, and astragalus, [and to the patella by the liga- mentum patellae;] its ossification commences in three points, one for the shaft, and one for each extremity, the tubercle at the upper end of the crest, and the malleolus are sometimes found as epiphyses. [This bone may be fractured at almost any point of its shaft, but is most liable to break at the thinnest part, the junction of the mid. die and lower thirds ; one of the condyles may be fractured off ob- liquely, and sometimes the malleolus internus is broken off. Muscles. Ten are attached to this bone ; five arise from it ; the tibialis anticus and extensor longus digitorum from its anterior sur- face ; the soleus, tibialis posticus, and flexor longus digitorum from its posterior surface : five are inserted into it ; the sartorius, gracilis, and semitendinosus into the upper part of its inner face ; the semi- membranosus and popliteus into its upper and back part.] The fibula is very slender and nearly as long as the tibia ; it is placed at the side of the leg, nearly vertical, its lower end inclined a little forwards ; the superior or femoral end is small and circular, and presents a slight cavity forwards, upwards, and inwards, to articulate with the tuberosity on the external condyle of the tibia, behind this is a slight py- ramidal projection, [the styloid process,'] its whole circum- ference is rough for the insertion of ligaments which attach it to the tibia, also for the external lateral ligament of the knee joint, and for the tendon of the biceps ; below this the bone is round and slender like a neck ; the body then becomes triangular ; is a little curved backwards and inwards above, but is twisted forwards below ; this [the in- ternal surface] is divided into two portions by the internal edge into which the interosseous ligament is inserted, the anterior portion gives attachment to the extensors, and the posterior, which is larger, is grooved for the tibialis posti- cus, its external surface is covered by the peronsei muscles, DUBLIN DISSECTOR. 469 the posterior surface gives attachment to the solaeus above and to the flexor pollicis below ; in this surface we perceive the orifice of the vascular canal leading downwards; the internal edge, which is turned a little forwards, gives at- tachment to muscles above and to the interosseous ligament elow, the external edge is turned backwards, and gives ttachment to the solasus, flexor pollicis, and peronaei mus- lus ; and the anterior sharp edge to the extensor digitorum nd to the peronsei; inferiorly this edge turns outwards nd bifurcates, enclosing a triangular surface, which is ubcutaneous: the lower or larsal end is larger than the ead, it is elongated into a long oval process, the external mlleolus or ankle ; this is larger, more prominent and pos- rior to the inner ankle, it is convex and subcutaneous ex- ernally, internally it is smooth and triangular, a little con- ave from behind forwards, and convex in the perpendicu- ar direction, it articulates with the astragalus ; above this 3 a triangular rough surface to articulate with the tibia, nteriorly this process is rough but thin for the origin of gaments, its posterior edge is broader and grooved for the eronteal tendons, internal to which is a depression for the rigin of the posterior external lateral ligament of the nkle joint ; from the point of this process the external ateral ligament arises; the fibula is articulated at both nds to the tibia and below to the astragalus. [This bone may be broken either alone or with the tibia, being nost liable to fracture at the junction of the middle with the lower lird ; it is often broken in conjunction with a wrench at the ankle oint. The malleolus externus may be broken off. Muscles. Nine muscles are attached to this bone ; eight arise cm it ; the peronei longus and brevis from its external surface ; the xtensor longus digitorum, extensor pollicis proprius, and peroneus ertius in front of the interosseous ligament ; the tibialis posticus be- ind it, all from the internal surface : the soleus and flexor pollicis ongus, from its posterior surface ; one muscle only is inserted into the biceps flexor cruris at its styloid process and head.] The foot is divided into the tarsus, metatarsus, and toes, 'he bones of the tarsus are seven, astragalus, calcaneum, lavicular, cuboid, and three cuneiform. The astragalus is next to the calcaneum in point of size, t is of an irregular twisted shape, somewhat cubical, larger ibove and to the outside, than internally or posteriorly ; it situated at the upper and middle part of the tarsus, where t is wedged between the two malleoli, its superior surface )resents in its two posterior thirds a large pulley-like articu- ar surface, which is convex from behind forwards, and ioncave transversely, the reverse of the form of the end of he tibia, it is inclined a little backwards, is broader before 40 470 DUBLIN DISSECTOR. than behind, and more prominent externally than inter- nally ; anterior to this surface is a rough depression, on the neck of the bone, for the insertion of ligaments ; inferiorly, it presents two articular surfaces for the os calcis, one 'is posterior and external, broad and concave, the other is an- terior and internal and convex ; these surfaces are sepa- rated by a deep groove, which is narrow behind, broad be- fore, and directed forwards and outwards ; strong ligaments pass from this groove to the os calcis ; the posterior surface of the astragalus is narrow and slightly grooved in an ob- lique direction downwards and inwards, for the tendon of the flexor pollicis ; it also presents externally a pointed eminence to which the external lateral ligament of the ankle joint is attached' ; the anterior extremity is a smooth round head, supported by a sort of neck, which is perforated by many small holes for vessels, it is directed forwards, in- wards, and downwards, and is articulated with the navicu- lar bone ; the external side presents a triangular, smooth surface, concave from above downwards, and a little con- vex from before backwards, it is articulated with the fibula ; the inner side is rough for ligaments, except a cartilaginous Surface near the upper part, which is smaller than that on the outer side, and broader before than behind, this is ar- ticulated with the internal malleolus. The calcaneum or os calcis is the largest bone in the tar- sus, at the lower and posterior part of which it is placed, it is elongated posteriorly into a process called the heel, its upper surface presents two articulating surfaces to sup- port the astragalus ; the posterior is convex, broad, and di- rected forwards and out'wards, the anterior is internal, nar- row and concave ; these are separated by a deep, rough, transverse groove into which strong ligaments are inserted ; internal to this the bone is uneven, and projects into a sort of process, into which the internal lateral ligament of the ankle joint is inserted ; the inferior surface is smaller than the superior, and is nearly flat, it presents small tubercles for the attachment of muscles and ligaments ; the posterior extremity is slightly convex, smooth above and covered by a bursa, and rough below for the insertion of the tendo Achillis ; the anterior extremity is smaller, and presents an articular surface for the cuboid bone, which is concave from above downwards, and convex from side to side ; ex- ternally it is rather flat, being marked with two shallow grooves, for the peronrcal tendons, a spine separates these, into this the external lateral ligament of the ankle joint is inserted, internally it is broad and hollowed out into an arch, inider which the flexor tendons, the tibialis posticus and the plantar vessels and nerves pass, the tendon of the DUBLIN DISSECTOR. 471 flexor pollicis runs in a distinct groove ; the os calcis is at- tached above to the astragalus and before to the cuboid. [The groove for the tendon of the peroneus longus is sometimes converted into a large osseous pulley, projecting about three lines from the body of the bone ; of this I have two specimens from the same subject. Muscles. Nine are attached. to this bone; six arise from it; the extensor digitorum brevis from its upper and outer part; abductor pollicis, abductor minimi digiti, flexor brevis digitorum, flexor acces. sorius, and flexor brevis pollicis infcriorly from its tubercles and mar- gins ; three are inserted .into it, the gastrocnemius, soleus, and plan, taris posteriorly.] The navicular or scaphoid bone is situated about the middle of the tarsus and at its upper and internal part ; of an oval form, its long axis directed downwards and inwards, its posterior surface. is smooth and concave, to form a sort of superficial or glenoid cavity for the head of the astragalus, the latter, however, is much larger and projects inferiorly, in which direction it is supported by the strong calceo-scap- hoid ligament, and by the tendon of the tibialis posticus, which here generally contains a sesamoid bone ; the ante- rior surface is convex, and divided by two vertical ridges into three* surfaces for the three cuneiform bones ; the cir- cumference is irregular for the attachment of ligaments, in- ternally it is rather smooth, but inferiorly it presents a tubercle into which the tibialis posticus is inserted ; on its external side there is in general a small, Hat articular surface for the cuboid bone ; the scaphoid is connected to five bones, viz. the astragalus, the three cuneiform, and the cuboid. [Muscles. One, the tibialis posticus is inserted into this bone.] The cuboid bone is situated at the outer and anterior part of the tarsus external to the navicular, and anterior to the calcaneum ; although of a cubical form, it is yet thicker and longer internally than externally, its upper surface is flat and rough for the attachment of ligaments and muscles, the lower surface is irregular, rough, and tubercular, be- hind for the calceo-cuboid ligament, and grooved before for the tendon of the peronoeus longus, its posterior surface is smooth, concave transversely, but convex from above down* wards, this slightly pulley-like surface is articulated with the calcaneum, anteriorly it presents two articular surfaces, the internal is square and supports the fourth met a tar Sal bone, the external is triangular and supports the fifth ; the external side is narrow, the internal is rough posteriorly, but presents anteriorly two articulating surfaces, the poste- rior for the scaphoid, and the anterior for the external cu- neiform bone ; the cuboid is articulated with the calcaneum, 472 DUBLIN DISSECTOR. the scaphoid, the external cuneiform, and the two external metatarsal bones. [Muscles. Several of the small muscles of the foot, to some extent arise from this bone, as the extensor brevis digitorurn superiorly, and the flexor brevis pollicis, adductor pollicis, and flexor brevis minimi digiti inferiorly.] The cuneiform bones : these three wedge-shaped bones are situated at the anterior part of the tarsus, between the scaphoid and the three internal metatarsal bones ; the first or the internal is the largest of the three, its base is below, and its long axis is from above downwards, it is articulated posteriorly to the scaphoid bone, anteriorly to the first and externally to the second metatarsal bone, and to the middle cuneiform, inferiorly its presents a tubercle for the inser- tion of the tibialis anticus, and for a portion of the tendon of the tibialis posticus ; the middle cuneiform is the smallest, and is wedged in between the two others ; it is also articu- lated behind to the scaphoid and before to the second me- tatarsal bone ; the third or external cuneiform bone is situ- ated between the last and the cuboid bone, it is articulated anteriorly with the third metatarsal bone : posteriorly with the scaphoid, internally with the middle cuneiform and with the second metatarsal bone, and externally with the cuboid, and with the fourth metatarsal bone. [Muscles. The libialis anticus and posticus are inserted; the first internally, the second inferiorly into the internal cuneiform bone ; and the flexor brevis pollicis arises somewhat from the others.] All the bones of the tarsus are composed of a soft, spon- gy, vascular tissue covered by a compact but thin lamina ; they are each developed from one point of ossification, ex- cept the calcaneum and the astragalus, which commence each in two points. The metatarsal bones are five in number, the first or inter- nal is the shortest and thickest, convex above, concave and sharp below, its posterior end is oval, concave, and rests on the internal cuneiform bone, the anterior end round and smooth, supports the first or great toe, this extremity is grooved below, and lodges the sesamoid bones, the pero- na3us longus is also inserted into it ; the second is the long- est of the metatarsal bones, its tarsal end is wedged in be- tween the three cuneiform bones, and is articulated to each of them; the outer side of its base is also joined to the third metatarsal bone, its anterior extremity or head is round, and supports the second toe, it is marked internally and exter- nally by the depressions for the lateral ligaments, a groove separates the head from the body of the bone ; the third metatarsal bone is a little shorter than the second, but of the DUBLIN DISSECTOR. 473 same form ; its base rests on the third cuneiform bone ; the fourth metatarsal bone is a little shorter, it rests on the cu- boid bone, and the inner side of its base also rests against the third cuneiform bone ; the fifth is the shortest except the first, it rests on the cuboid bone ; the heads of all the metatarsal bones are round like those of the metacarpus, the bases flat to articulate with the tarsus, the sides of their bases are also flat to join one another ; all these bones possess a similar structure, and resemble the class of long bones. ( The toes are five in number, the first or the great toe has only two phalanges, all the others have three ; there are, therefore, fourteen phalanges in all ; \hejirst phalanges are longest, they are convex above, concave below ; their pos- terior end is larger and presents, as in the hand, a round concavity for the head of the metatarsal bone ; the ante- rior end is convex from above downwards, and concave from side to side, so as to form a ginglymoid joint with the second phalanx. The second phalanges are very short, the great toe has none, the posterior end of each is concave from above downwards, but convex transversely, being di- vided by a vertical ridge ; the anterior extremity is smaller than that of the first phalanx, its condyles are less promi- nent. The third phalanges are all very small except that of the great toe, they are of a pyramidal form, and support the nails, their posterior extremity being very large and similar to that of the middle phalanges, their anterior end is tubercular and attached to the cellulo-vascular texture at the extremity of each ; at the base of the first phalanx of the great toe there are in general two sesamoid bones into which the small muscles of this toe are inserted, frequently also there is another at the base of the second phalanx, sometimes one is found at the first joint of the second toe, and another at that, of the fifth. [Muscles. All the small muscles of the foot are inserted into the metatarsal and phalangeal bones ; besides which the peroneus longua is inserted into the metatarsal bone of the great toe, and the peronei brevis and tertius into that of the fifth toe ; the flexor longus digito. rum, flexor longus pollicis, extensor longus digitorum, and extensor proprius pollicis are inserted superiorly and inferiorly into the last phalangeal bones. The bones of the tarsus an* sometimes fractured, but only by great violence ; the metatarsal and phalangeal bones are not often broken.] THE SUPERIOR EXTREMITIES. EACH superior or thoracic extremity consists of the shoulder, arm, forearm, wrist and hand; the whole limb comprises thirty-two bones, the sesamoid not included : the shoulder 40* 474 DUBLIN DISSECTOR. is composed of the clavicle and scapula ; the arm of the humerus ; the fore arm of the radius and ulna ; the wrist of the eight small carpal bones; the hand of the five meto- carpal and fourteen phalangeal bones. The clavicle extends from the summit of the sternum ob- liquely across the first rib, upwards, backwards, and out- wards to the acromion process of the scapula, it is curved somewhat like an italic/, particularly in the male, in the female it is straighter and longer ; it consists, like all long bones, of two extremities and a body or shaft. The inter- nal or sternal end is thick, it presents a triangular articula- ting surface, inclined forwards and downwards, convex from above downwards, concave from before backwards, large above and before, small and pointed below and be- hind, the circumference is rough for the attachment of li- gaments. The body is nearly cylindrical towards the ster- nal, but flat and 'expanded towards the acromial end, smooth above and mostly subcutaneous, inferiorly it is rough and presents about an inch from the sternal end a ridge or process for the rhomboid or costo-clavicular liga- ment, external to this is a groove for the subclavian muscle, in this also is a foramen for the nutritious vessels, and near the scapular end is a rough ridge leading backwards and outwards for the attachment of the coraco-clavicular liga- ments ; its anterior edge is convex in the inner half, and gives attachment to the great pectoral muscle ; the outer half is concave, to it the deltoid is attached ; the posterior is smooth and concave in the inner half towards the great vessels, and rough and convex externally for the attach- ment of the trapezius muscle. The acromial end of the cla- vicle passes over the coracoid process upwards and back- wards, is flat and broad, rough above and below, and per- forated by vessels ; it presents at its termination a small ar- ticulating surface for the acromion scapula? ; this surface is oval from before backwards, and cut obliquely from above and from without downwards and inwards, its aspect is outwards, forwards and downwards, so that it rather rests on or over the articulating surface of the acromion sea- puke, its circumference is rough for the attachment of liga- ments. The clavicle serves to support the scapula, and to prevent it from falling too much forwards or inwards, it thereby allows it a greater freedom of motion, it also serves as a fixed point for certain muscles, and it protects the ves- sels and nerves of the upper extremity ; it is very perfect in the foetus, and is developed from a single point of ossi- fication ; it has no perfect epiphysis, although in the young subject there is an osseous crust at each extremity, which is at first separable from the rest of the bone. DUBLIN DISSECTOR. 475 [This bone is the common seat of fracture, which usually occurs in its middle third. This bone has been successfully removed, both in part and in whole. Muscles. Six are attached to this bone ; four arise from it ; the sterno-rnastoid and sterno-hyoid from its sternal end ; the pectorali.s major and deltoid from its anterior border; two are inserted into it, the trapezius posteriorly, and subclavius inferiorly.] The scapula is situated at the upper, lateral and posterior part of the chest, and extends from the second to the sev- enth rib, it is irregularly flat and triangular, it presents an internal and an external surface, three edges and three an- gles. The internal or anterior surface or subscapular fossa looks towards the ribs, is slightly concave, and divided by three or four prominent lines which run obliquely from above downwards, and from without inwards into several broad grooves, which are filled by the fasciculi of the sub- scapular muscle, the aponeurosis of which is attached to those ridges ; above and below these is a smooth flat sur- face to which the serratus magnus is attached. The ex- ternal or posterior surface or the dorsum is divided trans- versely into two unequal parts by a ridge or spine which commences about the upper third of the posterior border of the scapula, from a smooth, polished, flat, triangular sur- face, it proceeds forwards and becomes more elevated, flat- tened above and below, and bounded by a long, irregular, undulated margin, which is rough above for the attach- ment of the trapezius, and below for that of the deltoid muscle, a vascular hole is observed on its upper and under surface : this spine is a little contracted anteriorly and ex- ternally, and terminates in an eminence named the acro- mion process ; this surmounts the shoulder joint, about an inch above it, is flattened in a direction contrary to that of the spine, its external surface looks a little upwards and backwards, is convex, rather rough and covered by the in- teguments, its inferior or internal surface is smooth and concave, its upper edge is directed backwards, gives at- tachment to the trapezius, and presents near its termination a small and nearly horizontal, oval, articulating surface for the clavicle, the aspect of this surface is a little oblique upwards, inwards and backwards ; the lower edge gives attachment to the deltoid, its apex is rounded for the inser- tion of the triangular, or coraco-acromial ligament. Above the spine is the supra-spinata fossa, which is wider behind than before, this is filled by the supra-spinous muscle ; the fossa infra-spinata is larger, is convex above and concavt and grooved inferiorly ; between this and the inferior cost- is a raised surface extending from the inferior angle to the glenoid cavity ; this surface is divided into two by an ob- 476 DUBLIN DISSECTOR. lique line, the posterior portion is flat and somewhat square, and gives attachment to the teres major muscle, the ante- rior to the teres minor ; into the ridge between these is in- serted an aponeurosis common to these two muscles. The superior or cervical costa or border of the scapula is the shortest and thinnest ; at its forepart is a [semilunar] notch which is converted into a hole by ligament and sometimes by bone ; it is traversed by the supra-scapular nerve, and sometimes by the vessels of that name, to this costa, the supra-spinatus, subscapular and omo-hyoid muscles are attached. From the anterior part of this border in front of the notch arises the coracoid process, which is long and nar- row, and directed at first upwards and forwards and then downwards, is convex and rough above for the attachment of the conoid and trapezoid ligaments, smooth and concave below ; it overhangs the inner and upper part of the gle- noid cavity, the pectoralis minor is inserted into it ante- riorly, the biceps and coraco-brachialis into its summit, and the triangular ligament into its external border. The base of the scapula or the posterior or vertebral edge is nearer the spine above than below; the spinati muscles adhere to its outer lip, the subscapular to its inner, and the rhomboid to its middle ; about one-fourth from its upper extremity is a blunt projection formed by the smooth trian- gular root of the spine ; at the union of the base and upper costa is the superior posterior angle, which is embraced by the levator anguli muscle. The anterior or inferior or ex- ternal or axillary costa is very thick, and inclines down- wards and forwards, at its junction with the base it forms the inferior angle, on which is a long flat surface which gives origin to the teres major, and to a few fibres of the latissimus dorsi muscle ; to the upper part of it the long head of the triceps is attached; at the convergence of this and of the superior costa, the glenoid cavity and the neck of the scapula are situated. The neck is that contracted portion, which gives attachment to the capsular ligament, it is most distinct externally and inferiorly. The glenoid cavity is superficial, oval, broader and deeper below, cover- ed with cartilage, and in the recent subject deepened by the fibrous glenoid ligament, which is chiefly derived from the long tendon of the biceps, which is attached to the up- per extremity of this cavity ; it is inclined a little down- wards, outwards and forwards, its aspect however varies, as the scapula is made to turn in all the rotatory motions of the arm. The scapula is composed of two compact la- minae and an intervening cellular tissue, the latter prevails in the processes, the neck and the inferior angle ; in the middle of the fossae there is but little of it, and the compact DUBLIN DISSECTOR. 477 substance is there thin and transparent. The scapula is developed by several points of ossification, one in the cen- tre of the body, one for each of the processes, one for the inferior angle and one for the posterior or vertebral edge. [This bone may be broken in its body, either by gun-shot wounds or blows ; the acromion process may be broken ; and fracture of the neck may occur, and be confounded with fracture of the neck of the os brachii or dislocation of that bone. Muscles. Sixteen are attached to this bone ; ten arise from it ; the supra and infra spinatus, arid subscapularis from the several fos- sro of the same name and their edges ; the omo-hyoid from over the semilunar notch; the teres major and minor, and long head of the triceps extensor cubiti, from the anterior margin : the deltoid from the lower edge of the spine and acromion ; the Jong head of the biceps flexor from the apex of the glenoid cavity and ; its short, head, and the coraco-brachialis from the coracoid process ; six are inserted into it ; the trape/ius into the upper edge of the spine ; the levator anguli scapulae into the superior angle.; the rhomboidei major and minor, and serratus magnus anticus into the base, and pectoraiis minor into the coracoid process.] The os humeri is attached to the scapula above and to the radius and ulna below ; it is the longest and largest bone in the upper extremity, it presents two extremities and a body or shaft ; the upper or scapular extremity is the larger, it consists of the head, neck and two tubercles. The head is semi-spherical, inclined upwards, inwards and backwards, smooth and covered with cartilage for articulat- ing with the glenoid cavity of the scapula. The?iec/c is the slightly contracted line around the head, it is rough for the attachment of the capsular ligament, and a little longer be- low and liefore than above or behind ; the axis of the neck and head forms an obtuse angle with that of the shaft. The tuberosities are two, the greater or lesser ; thegrea/ or ex- ternal is also posterior, it is round, and presents three depres- sions ; to the anterior of these the supra-spinous muscle is attached, to the middle the infra-spinous and to the posterior the teres minor. The internal or lesser tuberosity is also ante- rior, it is more prominent, and gives insertion to the subsca- pular tendon ; between these tubercles is the deep groove for the long tendon of the biceps, into the anterior or outer edge of which the tendon of the great pectoral is inserted, and into its posterior or inner those of the teres major and la- tissimus dorsi, this groove leads downwards and inwards. The body or shaft of the humerus is thick and round above, twisted in the middle, expanded and somewhat triangular inferiorly ; its posterior surface is round above and twisted a little inwards, below it looks outwards and is flat and broad ; this surface is covered by and gives attachment to 478 DUBLIN DISSECTOR. the triceps muscle, a small vascular foramen may be ob- served about the centre. The anterior surface is divided for about one-fourth of its length by the bicipital groove into two unequal portions, the internal of which is smooth, and presents near its centre a lineal elevation for the in- sertion of the coraco-brachialis, in the lower part of which is an oblique vascular foramen; the external portion is rough above for the insertion of the deltoid muscle, a-nd is grooved obliquely below for the passage of the musculo- spiral nerve and artery ; these surfaces are separated by two prominent lines, one is external and anterior, the other is internal and posterior, these lines are more distinct be- low than above, they give attachment to the inter-muscular ligaments, and lead down to either condyle; the external is interrupted about the middle by the musculo-spiral groove, but is very prominent below, curved forwards, and gives attachment to the brachialis anticus, the supinators and extensors, the triceps and the external intennuscular ligament ; on the anterior surface of the humerus there is also a prominent line continued from the anterior edge of the bicipital groove, it is gradually flattened below, and covered .by the brachialis anticus muscle. The lower extremity of the humeris is flattened, elongated transversely, and twisted a little forwards, it presents in- ternally the internal condyle, which is very prominent and turned somewhat backwards ; this gives attachment to the common tendon of the pronators and flexors, and to the in- ternal lateral ligament of the elbow joint; externally is the external condyle, not so prominent as the internal, and situ- ated lower down, it gives attachment to the external lateral ligament, and to the supinator and extensor^ muscles. Between and below these condyles is an articulating sur- face turned forwards and presenting externally a small round head which articulates with the radius, above and in- ternal to which is a slight depression corresponding to the margin of the radius, internal to this is a sharp semicircu- lar ridge which separates the radius and ulna, and next to this is the trochlea for articulation with the ulna, this is so much below the level of the small head and of the outer portion of the articular surface, as to give the whole bone an oblique direction outwards when its lower end is placed on a horizontal plane ; at the anterior extremity of this trochlea is a small depression for the reception of the co- ronoid process in flexion of the joint, and at the posterior is a large fossa which lodges the olecranon process in the extended state of the fore arm. [The anterior and posterior semilunar cavities which sometimes DUBLIN DISSECTOR. 479 communicate through a perforation in the bone ; this is said to occur most frequently in the negro.] The humerus, like the femur, is compact in the structure of its body, and cellular in that of its extremities, it con- tains a large medullary canal, and is developed from eight points of ossification, one for the head, one for each tube- rosity, one for the shaft, one for the trochlea, one for the small head, and one for each condyle. [This bone may be fractured between the head and tuberosities, or beneath the tuberosities, or at any point of its shaft, or lastly one of the condyles may be broken off. Muscles. Twenty-four are attached to this bone ; fifteen arise from it; the middle and short heads of the triceps extensor and brachialis anticus from the shaft ; the supinatores radii longus and brevis, extensores carpi radialis longior and brevior, extensor carpi ulnaris, extensor communis digitorum, extensor minimi digiti, and anconeus from the external condyle and ridge leading to it ; the pro. nator radii teres, flexor carpi radialis, flexor carpi ulnaris, palmaris longus, and flexor sublimis digitonim from the internal condyle and ridge leading, to it. Nine are inserted into it ; the subscapularis into the lesser tuberosity ; the supra and infra spinati and teres minor into the greater tuberosity ; the pectoralis major into the anterior lip of the bicipital groove ; and the teres major and latissimus dorsi into its posterior lip ; the coraco-brachialis and deltoid into the shaft.] The ulna is situated at the inner side of the fore arm, it is longer than the radius, and is divided into the body and two extremities; the upper extremity is larger than the lower, and presents two processes and an intervening ca- vity. The posterior process, or the olecranon, is the highest part of the bone, its superior border gives attachment to the triceps extensor ; posteriorly it presents a smooth tri- angular surface, covered hy skin and by a bursa, anteriorly it is concave and covered with cartilage.. The coronoid pro- cess is anterior and inferior to the preceding, anteriorly it gives insertion to the brachialis anticus muscle, internally to the flexors and pronators, and to the internal lateral liga- ment, and externally it is hollowed out into the lesser sig- moid cavity, which receives the head of the radius ; this cavity is oval, its greatest diameter being from before backwards, it leads superiorly into the great sigmoid cavity, which moves on the trochlea of the humerus in flexion and extension of the fore arm ; this sigmoid cavity has a great resemblance to the letter C, if viewed in profile ; its pos- terior vertical portion is larger than the anterior horizon- tal ; it is divided by a middle ridge into two lateral por- tions, of which the internal is the larger; these are each again divided by a transverse furrow, which ends in a notch at either margin, this surface is all covered with car- 480 DUBLIN DISSECTOR. tilage, except the furrow, in which some fatty matter is lodged. The body of the ulna is divided into three surfaces by three lines ; these surfaces are larger above than below ; the anterior is slightly grooved for the flexor profundus, and presents superiorly a vascular foramen, directed ob- liquely upwards; the internal surface is broad and con- cave above, and covered by muscles, below it is round and subcutaneous : the posterior surface is irregular ; it is di- vided into two portions by a prominent line ; of these the superior and internal is broad, and gives attachment to the anconseus ; the inferior and outer portion is long and nar- row, and covered by the extensors of the thumb ; the an- terior edge is round and gives insertion to the flexor pro- fundus and pronator quadratus ; the posterior edge is very distinct above, and gives attachment to an aponeurosis, common to the flexor profundus and flexor and extensor carpi ulnaris ; the external edge is sharp for the three su- perior fourths, and gives attachment to the interosseus lig- ament. The lower or carpal end of the ulna is small and round, and presents two eminences ; the external is named the head, it is round and covered with cartilage, and is re- ceived into the cavity in the inner border of the radius, and is contiguous inferiorly with the nbro-cartilage of the wrist; the internal eminence or the styloid process is more prominent, and on a level with the posterior surface of the bone ; it is conical, elongated and a little everted ; it gives attachment to the internal lateral ligament of the wrist; these processes are separated posteriorly by a groove for the tendon of the extensor carpi ulnaris, and inferiorly by a depression for the insertion of the triangular nbro-carti- lage. The ulna is articulated above to the humerus and radius, and below to the radius, and inter-articular carti- lage ; it is developed from three points of ossification, one for the shaft, and one for each extremity. [This bone may be broken either alone or with the radius at almost any point of its shaft ; the olecranoa or the coronoid process may be broken off. Muscles. Fourteen are attached to this bone ; eleven arise from it; the flexor carpi ulnaris, pronator radii teres, flexor sublimis digi- torum, flexor profundus digitorum, and pronator radii quadratus an- teriorly ; extensor carpi ulnaris, extensor ossis metacarpi pollicis, ex- tensores primi and secundi inter-nodii pollicis, extensor indicis, exten- sor digitorum communis posteriorly ; three are inserted into it ; the triceps extensor into the olecranon ; the brachialis anticus into the coronoid process, and the anconeus into the upper and back part.] The radius is shorter than the ulna by the length of the olecranon ; it is situated at the outer and anterior part of fore arm, is larger below than above, is curved about the DUBLIN DISSECTOR. 481 centre, and is convex outwards and backwards ; it is di- vided into the body and two extremities; the upper or humeral end presents a head, neck, and tubercle. The head is a circular superficial cavity, its surface and most of its circumference covered with cartilage ; the former to arti- culate with the small head of the humerus, and the latter with the sigmoid cavity of the ulna, and with the annular or coronary ligament ; the internal or ulnar portion of the circumference is broader than the external. The neck is about an inch long, it descends obliquely outwards, it is contracted and circular; at its lower extremity is the tul-.ir- de, this process is directed backwards and inwards, into its external rough surface the tendon of the biceps is in- serted; anteriorly it is smooth, and covered by a bursa. The body or shaft of the radius is somewhat triangular, and presents three surfaces, separated by three margins or an- gles ; the anterior surface is broad below and covered by the pronator quadratus, narrow above where it gives at- tachment to the flexor pollicis ; about one-third from the head is the orifice of the vascular canal, slanting obliquely upwards; the posterior surface is convex above and co- vered by the supinator brevis, concave in the middle for the extensors of the thumb, and convex below ; the exter- nal surface is round and convex, and presents near the centre a rough surface for the insertion of the pronator teres ; of the angles or edges the inner is most distinct ; it is sharp, and gives attachment to the interosseous ligament. The lower or carpal end of the radius is square, its anterior prominent edge gives attachment to the anterior carpal ligament , posteriorly it presents three grooves for the ex- tensor tendons ; one nearly in the middle line, narrow and obliq- ,e, lodges the tendon of the extensor secundi inter- nodii pollicis, the second is at the ulnar side of this, is broad, and transmits the tendons of the extensor communis and indicator, and the third, which is to the radial side of the first, is divided into two for the tendons of the extensor carpi radialis, longus and brevis ; along the external bor- der of this bone, is another groove leaning downwards and forwards, and divided into two for the extensor ossis meta- carpi and primi internodii pollicis ; the border between these two last grooves is prolonged down into the styloid process, from which the external lateral ligament of the wrist arises ; on the internal border is an oblong smooth cavity, to receive the lower end of the ulna; inferiorly the radius presents an articular surface, divided by a line from before backwards, into two unequal portions ; the external is large and triangular, and meets the scaphoid bone ; the internal is smaller, somewhat square, and meets the lunar 41 482 DUBLIN DISSECTOR. bone. The radius, like other long bones, is of a cellula structure at each extremity and compact in the centre, where it also contains a medullary canal, which is larger above than below ; it is developed from three points of os- sification, one for the shaft and one for each extremity. [Fractures of this bone, alone or with the ulna may occur at any point of the shaft ; more frequently both bones are broken be- low the middle ; fracture of the neck of the radius is very rare, and when occurring, unites by fibro-ligamentous substance. I have a specimen of this fracture and mode of union. Muscles. Nine are attached to this bone ; four arise from it ; flexor sublimis digitorum, flexor longus pollicis from its anterior sur- face ; extensor ossis metacarpi pollicis, and extensor primi inter-nodii posteriorly ; five are inserted into it ; the biceps flexor into the bici- pital protuberance ; supinator brevis and pronator teres into the mid. die of the outer surface, pronator quadratus into the lower part of its anterior edge, and the supinator longus into the outer surface low down.] The hand consists of the carpus, metacarpus, and fin- gers. The carpus is composed of eight bones, arranged in two rows ; the first row consists of the scapoid, lunar, cuneiform and pisiform ; the second of the trapezium, trapezoid, mag- num and unciform ; enumerating them from the radial to the ulnar side, or from without inwards. The scaphoid or navicular is the largest in the upper row, at the radial or outer side of which it is situated ; it presents four articular surfaces ; it is elongated and convex on the upper or radial surface, adapted to the external depression on the end of the radius; the inferior surface, directed a little outwards and backwards, is triangular, smooth and convex, to articulate with the trapezium and trapezoides; into the posterior narrow surface, ligaments are inserted ; to the external or radial side, the external lateral ligament is attached ; the inner or ulnar side presents two smooth articulating surfaces; one superior, narrow, to articulate with the lunar bone ; the other inferior, large and concave, to articulate with the head of the magnum : it thus meets five bones. [Muscles. Three arise from this bone, the abductor pollicis, oppo- nens pollicis, and flexor pollicis brevis.] The lunar or semicircular bone is smaller than the scap- hoid ; it presents four articulating surfaces; smooth and convex above to meet the radius, concave below to articu- late with the magnum and unciform : its ulnar side is flat to meet the cuneiform, and its external to meet the scap- hoid ; its anterior surface is larger than its posterior and DUBLIN DISSECTOR. 483 it projects a little into the palmar arch : it is articulated to five bones. The cuneiform, or pyramidal lone. The base of this wedge- shaped bone looks outwards and articulates with the lunar, the apex is inwards; it is convex and smooth above to meet the carpal fibro-cartilage ; concave and smooth below to articulate with the unciform bone ; rough posteriorly and internally for ligaments ; anteriorly it presents a flat circular cartilaginous surface for the pisiform bone; it is articulated to three bones and to the fibro-cartilage. The pisiform bone. This small pea-shaped bone is the smallest in the carpus, at the upper and inner part of which it is placed ; it is also on a plane anterior to the first row ; it is articulated to the cuneiform bone by a small circular surface ; its circumference is rough for the attachment of ligaments ; the flexor carpi ulnaris is inserted into it above, and the abductor minimi digiti [arises from it] below. The trapezium is the most external of the second row of the carpus ; it is concave above to meet the scaphoid, below it is convex from behind forwards and concave transverse- ly, to support the metacarpal bone of the thumb by a pul- ley-like surface; anteriorly it is marked with a groove for the tendon of the flexor carpi radialis; internally it is articulated to the trapezoid, and beneath this by a small surface to the second metacarpal bone: it joins four bones. [Muscles. Three are attached to this bone ; two arise from it, the abductor pollicis and flexor pollicis brevis ; and one is inserted into it, the extensor ossis metacarpi pollicis by one of its tendons.] The trapezoid is of a very irregular shape, and smaller than the trapezium ; above it is smooth and concave t> meet the scaphoid, externally it articulates with the trape- zium, internally with the rnagnum, and inferiorly with the second metacarpal bone : it joins four bones. The os magnum is the largest of the carpal bones ; it presents superiorly a round and hemispherical head, which is received into the socket formed by the scaphoid and lu- nar bones ; this head is supported by a contracted neck, its greatest convexity is turned backwards und outwards ; the inferior surface of the magnum is divided into three articulating surfaces ; these support the second, third, and fourth metacarpal bones ; that for the the third is the lar- gest, and for the fourth the smallest ; its posterior surface is broad and convex below, and a little concave above ; externally it joins the trapezoid, and internally the unci- form ; both anteriorly and posteriorly it gives attachment to the ligaments ; it articulates with seven bones. 4#4 DUBLIN DISSECTOR. [Muscles. One head of the flexor pollicis biu/is arises from this bone.] The unciform bone is next in size to the os magnum ; it is situated at the lower and inner part of the carpus, is rather wedge-shaped, the base below, articulated with the fourth and fifth metacarpal bones ; its upper surface is narrow, and meets the semilunar bone ; its external side joins the magnum, its internal the cuneiform ; its posterior surface is rough for ligaments ; from its anterior projects a small hooked process, curved outwards for the attachment of the annular ligament and some of the muscles of the little finger. [Muscles. Two arise from this bone, the flexor brevis minimi di- giti and adductor minimi digitL] All the bones of the carpus, like those of the tarsus, are composed of a loose spongy vascular tissue, invested by a thin compact lamina; they are developed each from a single point of ossification, except the unciform, which has two ; the pisiform is the latest to ossify. The metacarpal bones belong to the class of long bones ; they are five in number, are placed nearly parallel to each other, except the first or that of the thumb, which is on a plane anterior to the others ; the first is thick and short, the third is the longest. They are all concave on the pal- mar surface, convex on the dorsal, and large at each ex- tremity ; the posterior end is of an irregular figure ; the an- terior presents a round head ; the palmar surface of each is narrow, and presents a median prominent line ; the posteri- or surface of the first is convex, but on the second, third, and fourth, it presents a prominent longitudinal line, which bifurcates and forms the sides of a flat triangular surface, extending for near two-thirds of their length; into their edges the interossei muscles are inserted ; the dorsal sur- face of the fifth is divided by an oblique line diagonally, the outer portion is concave, and lodges the fourth interos- seous muscle, the inner convex and broad, and covered by the extensor tendon of the little finger. The carpal end or base of the first is -concave from be- fore backwards, and convex transversely, to articulate with the trapezium ; the base of the second is concave, and arti- culates with the trapezoides, and presents also externally a small smooth surface for the trapezium, and internally two smooth surfaces, one for the magnum, the other for the base of the third metacarpal; the base of the third is nearly plane, and rests on the magnum, and presents on either side articulating surfaces for the contiguous metacarpal bones ; the base of the fourth presents two articulating sur- faces, one for the magnum and one for the lioeiform ; on DUBLIN DISSECTr 485 the radial side two, and on the ulnar side one articulating surface, for the adjacent metacarpal bones; the base of the fifth presents a concave surface, directed outwards to arti- culate with the unciform ; its radial side articulates with he base of the fourth metacarpal bone. The anterior, or digital ends of all the metacarpal bones ate convex, their smooth surfaces are broader and extend further on the palmar than on the dorsal surfaces of each ; they are arti- culated with the bases of the first phalanges. The fingers are composed each of three phalanges, ex- cept the thumb, which has only two ; there are therefore fourteen phalanges in all 4 the JjrsZ, or those next the meta- carpus, are the largest, the third are the smallest, the second or middle are of an intermediate size. The metacarpal or the first phalanges are five in number ; the base or poste- rior end of each presents a cavity transversely oval for the head of the metacarpal bone ; the anterior extremity of each presents two small condyles, separated by a groove ; these are prolonged anteriorly, and articulate with the second or middle phalanx ; the anterior surface of each is arched from before backwards, hollowed from side to side, to lodge the flexor tendon, the sheath of which is attached to its late- ral edges ; the posterior surface is convex and arched. The second or middle phalanges are four in number, they are smaller than the first. ; the base of each presents two small cavities and a middle ridge, or a sort of pulley-like surface to articulate with the first, with which it forms a gingly- moid joint; about the centre of their anterior surface is a rough depression for the insertion of the teadon of the flexor sublimis ; the anterior or digital extremity of each resem- bles the anterior end of the first phalanx, and is convex from before backwards, and con-cave from side to side ; the two articulating condyles being prolonged on the palmar further than on the dorsal surface, so as to increase the ex- tent of flexion ; the thumb wants this second phalanx. The third or last or ungual phalanges are five in number, they are the smallest and somewhat of a pyramidal form, the base articulates with the second phalanx, and presents a pulley-like surface* having two small cavities and a middle ridge, such as the base of the second phalanx ; their pos- terior surface, convex, supports the nail, their anterior is rough and irregularly concave, for the attachment of the flexor tendon and ligaments ; its anterior extremity or apex is irregularly tuberoulated to support the extremity of the finger. The phalanges in structure resemble metacarpal bones ; the last or the u.ngual are more cellular, and have no medullary canal ; they are developed each from tw points of ossification, one for the shaft, and one for the an 41* 486 DUBLIN DISSECTOR. terior extremity ; the posterior end is continued from the shaft. [Muscles, All the small mnscles of the hand, except the palmaris brevis, are inserted into the metacarpal and phalangeal bones ; be. sides which the extensor ossis metacarpi polhcis is inserted by one of its tendons into the metacarpal bone of the thumb; the extensor carpi radtalis longus, and flexor carpi radialis into that of the index finger ; the extensor carpi radialis brevis into that of the middle fin- ger ; extensor carpi ulnaris, and flexor carpi ulnaris slightly into that : of the little finger, the flexor digitorum sublimis into the second pha- langes ; the flexor digitorum profundus, and flexor longus pollicis into the last phalanges ; the extensor digitorum coiwmunis into the second and third phalanges of the four fingers ; the extensor indicis into those of the index finger; the extensor digiti minimi into those of the little finger ; and the extensor primi internodii, and extensor se- cundi internodii pollicis into the first and last phalanges of the thumb. The carpal bones are not often broken, it requiring great violence to fracture them ; the metacarpal and phalangeal bones are more fre- quently broken than those of the feet, from being more exposed ; in cases of supernumerary fingers and toes we find additional phalan- geal bones, and sometimes a supernumerary metacarpal or tarsal bone; but naore cotmmonly one of these seems to spread or bifurcate, so as to sustain two toes ; this malformation is often hereditary.] On the fore part of the articulation between the meta- carpal bone and the first phalanx of the thumb there are generally two sesamoid bones, and sometimes one in the cor- responding joint of the index finger ; these bones, like those in the foot, as well as in other situations, where they are occasionally found, as behind the condyles of the femur, in the heads of the gastrocnemii muscles, &e. do not properly belong to the osseous system, they are rather accessories to the tendons of muscles ; they are found in the limbs only, and generally in the direction of flexion. They are developed from cartilage, which is deposited in tendinous or ligamentous structure, and which is very slow to ossify ; the patella has some resemblance to bones of this class, it is, however, more perfect, and is placed on the aspect of extension. The sesamoid bones serve to strengthen the ar- ticulations to which they are attached, they also increase the power of the muscles, by altering the direction of their tendons, and removing them further from the axis of the bone which they are intended to move. PART V, DISSECTION OF THE JOINTS. WHEN all the muscles, vessels, nerves, &e., have been dissected, the student may examine the anatomy of the joints ; different sections of these should be made, and when the principal soft parts are removed, they should be subjected to maceration for two or three days. T.he several parts of the osseous system when connected either by natu- ral or artificial media, constitute the skeleton ; the attach- ment between two or more bones is denominated an articu- lation or a joint, of which there are great varieties in the frame ; they may, however, all be reduced to three classes, the rnoveable or diarthrosis, the immoveable or synarthrosis, and the mixed or amphiarthrosis. 1. DJARTHROSIS, or the moveable, includes all the per- fectly moveable joints, and presents three species, viz. en- arlhrosis, arthrodia, gingtymus ; the first resembles the ball and socket ; the second is a modification of the first, the surfaces being nearly plane ; the third is the hinge or trochlea, and is more complex. 2. SYNARTHROSIS, or the immoveable includes four species, viz. suture, gomphosiz, schyndylesis, and sympliysis. Suture is the serrated interlocking observable between the bones of the head, in most instances the opposed edges are indented like the teeth of a saw, in some few they meet by rather plane surfaces, (harmonia,) and in others they are scaly, and one overlaps the other, (squamous suture.) Gomphosis is seen in the connexion between the teeth and their sockets, and schyndelesis between the vomer and the other parts com- posing the septum narium ; symphysis is seen in the pelvis, between the ossa ilii and the sacrum, and between the ossa pubis ; the last named example, however, is placed by some among the mixed articulations. 3. AMPHIARTHROSIS, or the mixed, include those cases in which the bones are connected by an Intervening substance, 488 DUBLIN DISSECTOR. and enjoy very obvious motion, as the bodies of the verte- bra^ &c. All the moveable articulations include several structures differing in use and organization, viz. the extremities of two or more bones, these are covered by cartilage ; a synovial membrane, covered by a fibrous capsule, or by accessory ligaments and fasciae, they may also contain inter-articular cartilages and ligaments, also reddish vascular adipose masses. The articular or incrusting cartilages adhere al- most inseparably to the ends of the bones, they are smooth and elastic, composed of fibres which are placed perpen- dicular to the bone, they are thickest on the most convex part of the heads of bones, and on the circumference of the articular cavities. The inter-articular cartilages or fibro-cartilagcs are very elastic, the fibrous tissue in some of them is very evident; many of these are attached to the circumference of the cavities forming the glenoid or cotyloid ligaments which serve to deepen the cavity, and to prevent the hard edges of the bones striking against each other; some inter-ar- ticular cartilages are moveable, as in the temporo-maxillary and knee joints, all these bodies serve either to deepen the cavities, or to attach the bones more closely, or to lessen shocks. Synovial membranes of joints